Debug log
First enable Debug mode in the add-on Config->Expert->Debug->Debug (on)
The option "Include full details/RAW retrieved data in Debug log" is not usually needed and will generate very large logs. Enable that only if specifically requested otherwise leave it off.
WARNING: The option "Include sensitive login data in debug log [DON'T POST PUBLICLY]" should always be off. Should be enabled only if absolutely necessary, but logs made with that option on should never be posted in a public place. If that option is enabled sensitive information/credentials will not be filtered out in the log.
Then follow the official steps in Kodi wiki https://kodi.wiki/view/Log_file/Easy
After debug logging is no longer needed disable debug mode in the add-on Config->Expert->Debug->Debug (off) and disable Debug logging in Kodi.
Having Debug mode enabled in the add-on settings might slow down add-on operations and is recommended to leave it on only while needed.