Pretty confident this will work, just gotta reboot to make sure

src/cascadia/TerminalApp/AppLogic.cpp

@@ -400,6 +400,30 @@ namespace winrt::TerminalApp::implementation
         ShowDialog(dialog);
     }
 
+    void AppLogic::_ShowKeyboardServiceDisabledDialog()
+    {
+        auto title = RS_(L"KeyboardServiceWarningTitle");
+        auto text = RS_(L"KeyboardServiceWarningText");
+        auto buttonText = RS_(L"Ok");
+
+        Controls::TextBlock warningsTextBlock;
+        // Make sure you can copy-paste
+        warningsTextBlock.IsTextSelectionEnabled(true);
+        // Make sure the lines of text wrap
+        warningsTextBlock.TextWrapping(TextWrapping::Wrap);
+
+        warningsTextBlock.Inlines().Append(_BuildErrorRun(text, Application::Current().as<::winrt::TerminalApp::App>().Resources()));
+        warningsTextBlock.Inlines().Append(Documents::LineBreak{});
+
+        Controls::ContentDialog dialog;
+        dialog.Title(winrt::box_value(title));
+        dialog.Content(winrt::box_value(warningsTextBlock));
+        dialog.CloseButtonText(buttonText);
+        dialog.DefaultButton(Controls::ContentDialogButton::Close);
+
+        ShowDialog(dialog);
+    }
+
     // Method Description:
     // - Displays a dialog for warnings found while loading or validating the
     //   settings. Displays messages for whatever warnings were found while
@@ -470,6 +494,11 @@ namespace winrt::TerminalApp::implementation
     void AppLogic::_OnLoaded(const IInspectable& /*sender*/,
                              const RoutedEventArgs& /*eventArgs*/)
     {
+        const auto keyboardServiceIsDisabled = !_IsKeyboardServiceEnabled();
+        if (keyboardServiceIsDisabled)
+        {
+            _ShowKeyboardServiceDisabledDialog();
+        }
         if (FAILED(_settingsLoadedResult))
         {
             const winrt::hstring titleKey = USES_RESOURCE(L"InitialJsonParseErrorTitle");
@@ -482,6 +511,52 @@ namespace winrt::TerminalApp::implementation
         }
     }
 
+    bool AppLogic::_IsKeyboardServiceEnabled()
+    {
+        if (IsUwp())
+        {
+            return true;
+        }
+
+        // If at any point we fail to open the service manager, the service,
+        // etc, then just quick return true to disable the dialog. We'd rather
+        // not be noisy with this dialog if we failed for some reason.
+
+        // Open the service manager. This will return 0 if it failed.
+        wil::unique_schandle hManager{ OpenSCManager(nullptr, nullptr, SERVICE_QUERY_STATUS) };
+
+        if (LOG_LAST_ERROR_IF(!hManager.is_valid()))
+        {
+            return true;
+        }
+
+        // Get a handle to the keyboard service
+        wil::unique_schandle hService{ OpenService(hManager.get(), L"TabletInputService", SERVICE_QUERY_STATUS) };
+        if (LOG_LAST_ERROR_IF(!hService.is_valid()))
+        {
+            return true;
+        }
+
+        // Get the current state of the service
+        SERVICE_STATUS status{ 0 };
+        if (!LOG_IF_WIN32_BOOL_FALSE(QueryServiceStatus(hService.get(), &status)))
+        {
+            return true;
+        }
+
+        const auto state = status.dwCurrentState;
+        if (state != SERVICE_RUNNING && state != SERVICE_START_PENDING)
+        {
+            // The service is off - return false
+            return false;
+        }
+        else
+        {
+            // The service is on - this is good.
+            return true;
+        }
+    }
+
     // Method Description:
     // - Get the size in pixels of the client area we'll need to launch this
     //   terminal app. This method will use the default profile's settings to do

src/cascadia/TerminalApp/AppLogic.h

@@ -85,6 +85,8 @@ namespace winrt::TerminalApp::implementation
 
         void _ShowLoadErrorsDialog(const winrt::hstring& titleKey, const winrt::hstring& contentKey, HRESULT settingsLoadedResult);
         void _ShowLoadWarningsDialog();
+        bool _IsKeyboardServiceEnabled();
+        void _ShowKeyboardServiceDisabledDialog();
 
         fire_and_forget _LoadErrorsDialogRoutine();
         fire_and_forget _ShowLoadWarningsDialogRoutine();

src/cascadia/TerminalApp/Resources/en-US/Resources.resw

@@ -1,17 +1,17 @@
 <?xml version="1.0" encoding="utf-8"?>
 <root>
-  <!-- 
-    Microsoft ResX Schema 
-    
+  <!--
+    Microsoft ResX Schema
+
     Version 2.0
-    
-    The primary goals of this format is to allow a simple XML format 
-    that is mostly human readable. The generation and parsing of the 
-    various data types are done through the TypeConverter classes 
+
+    The primary goals of this format is to allow a simple XML format
+    that is mostly human readable. The generation and parsing of the
+    various data types are done through the TypeConverter classes
     associated with the data types.
-    
+
     Example:
-    
+
     ... ado.net/XML headers & schema ...
     <resheader name="resmimetype">text/microsoft-resx</resheader>
     <resheader name="version">2.0</resheader>
@@ -26,36 +26,36 @@
         <value>[base64 mime encoded string representing a byte array form of the .NET Framework object]</value>
         <comment>This is a comment</comment>
     </data>
-                
-    There are any number of "resheader" rows that contain simple 
+
+    There are any number of "resheader" rows that contain simple
     name/value pairs.
-    
-    Each data row contains a name, and value. The row also contains a 
-    type or mimetype. Type corresponds to a .NET class that support 
-    text/value conversion through the TypeConverter architecture. 
-    Classes that don't support this are serialized and stored with the 
+
+    Each data row contains a name, and value. The row also contains a
+    type or mimetype. Type corresponds to a .NET class that support
+    text/value conversion through the TypeConverter architecture.
+    Classes that don't support this are serialized and stored with the
     mimetype set.
-    
-    The mimetype is used for serialized objects, and tells the 
-    ResXResourceReader how to depersist the object. This is currently not 
+
+    The mimetype is used for serialized objects, and tells the
+    ResXResourceReader how to depersist the object. This is currently not
     extensible. For a given mimetype the value must be set accordingly:
-    
-    Note - application/x-microsoft.net.object.binary.base64 is the format 
-    that the ResXResourceWriter will generate, however the reader can 
+
+    Note - application/x-microsoft.net.object.binary.base64 is the format
+    that the ResXResourceWriter will generate, however the reader can
     read any of the formats listed below.
-    
+
     mimetype: application/x-microsoft.net.object.binary.base64
-    value   : The object must be serialized with 
+    value   : The object must be serialized with
             : System.Runtime.Serialization.Formatters.Binary.BinaryFormatter
             : and then encoded with base64 encoding.
-    
+
     mimetype: application/x-microsoft.net.object.soap.base64
-    value   : The object must be serialized with 
+    value   : The object must be serialized with
             : System.Runtime.Serialization.Formatters.Soap.SoapFormatter
             : and then encoded with base64 encoding.
 
     mimetype: application/x-microsoft.net.object.bytearray.base64
-    value   : The object must be serialized into a byte array 
+    value   : The object must be serialized into a byte array
             : using a System.ComponentModel.TypeConverter
             : and then encoded with base64 encoding.
     -->
@@ -149,6 +149,12 @@
   <data name="SettingsValidateErrorTitle" xml:space="preserve">
     <value>Encountered errors while loading user settings</value>
   </data>
+  <data name="KeyboardServiceWarningTitle" xml:space="preserve">
+    <value>Warning:</value>
+  </data>
+  <data name="KeyboardServiceWarningText" xml:space="preserve">
+    <value>The "Touch Keyboard and Handwriting Panel Service" isn't running on your machine. This can prevent the Terminal from receiving keyboard input.</value>
+  </data>
   <data name="Ok" xml:space="preserve">
     <value>OK</value>
   </data>