White screen, no editor, 2 x errors in console

[willstocks]

Describe the bug
Hi guys,
I’m seeing two errors in Chrome’s dev console when trying to create a new post in 3.9 (WP 4.9.8, PHP 7.2):

Uncaught TypeError: Cannot read property 'primaryShift' of undefined at Object.217 (index.js:12) at n (index.js:1) at wp.editPost.0 (index.js:1) at index.js:1 217 @ index.js:12 n @ index.js:1 wp.editPost.0 @ index.js:1 (anonymous) @ index.js:1

and

Uncaught TypeError: Cannot read property 'initializeEditor' of undefined at HTMLDocument.<anonymous> (post-new.php:2448) (anonymous) @ post-new.php:2448

This happens why I try to create a new Gutenberg post.
I’m unsure if it relates to the following error I have reported with Yoast: https://wordpress.org/support/topic/yoast-gutenberg-cannot-read-property-pluginsidebar-of-undefined/

To Reproduce
Steps to reproduce the behavior:

1. Add new post
2. See white screen

Expected behavior
Expecting to see the Gutenberg editor.

Screenshots

Desktop (please complete the following information):

• OS: Windows 10 + macOS Mojave
• Browser: Chrome (latest standard for both macOS and Windows), Safari, Edge and IE11

Smartphone (please complete the following information):
N/A - haven't tried

[designsimply]

Thank you for including error details from your browser console!

I just tested installing Yoast 8.3 on a site running WordPress 4.9.8 and Gutenberg 3.9.0 and the editor loads normally for me so I may be missing a testing step or I may be missing a plugin or server config setting that you have that I do not. I tested from Firefox 62.0 on macOS 10.13.6 and the test site I used is hosted at WP Engine.

First, to confirm whether or not this is a plugin conflict with Yoast and Gutenberg in your case, could you temporarily disable Yoast and then clear browser cache and try starting a new post to see if the same exact errors show up in the console? If the errors go away, we'll know it's a plugin conflict with Yoast. If the errors are still there, could you please provide a list of your active plugins and note where your website is hosted?

In your screenshot, I see what looks like a lonely gray button at the bottom of the screen near the right side. What is that?

[willstocks]

Hi @tofumatt
I deactivated Yoast, and the Gutenberg editor loaded up immediately with no errors in the console.

RE: the little button, that was my mouse hovering over an icon on the system tray on my MacBook :)

[willstocks]

Have also notified the guys at Yoast @CarolineGeven per the issue I've logged there: Yoast/wordpress-seo#11131

[tofumatt]

Awesome, much appreciated! I'll close this issue then, thanks for following up with us and filing with Yoast!

[JohnGiddi]

Awesome, much appreciated! I'll close this issue then, thanks for following up with us and filing with Yoast!

Hello! What is the proof that Yoast causes the issue?
Greetings

[tofumatt]

As mentioned above:

I deactivated Yoast, and the Gutenberg editor loaded up immediately with no errors in the console.

[willstocks]

@JohnGiddi - also worth seeing the comment here: https://wordpress.org/support/topic/white-screen-no-editor-2-x-errors-in-console/#post-10754009 further to the above

[loorlab]

+1