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Languagetool not working with recently created Google Docs

The app does a fantastic job, except on any new Google Docs I create on my account. Lately, I always get this error message: No user found for given username [My Google ID] and given API key. On all previously created Google Docs, everything works 100%, but on none of the newly created Google Docs.
The LanguageTool for Windows desktop, the LT add-on for Thunderbird, for LibreOffice all work 100%, I can log into my Premium account, everything find. The error occurs only on recently created Google Docs.