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Your LimeSurvey version: Version 5.3.18+220530
Own server or LimeSurvey hosting: Self hosted
Survey theme/template: Varous
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This has been brought up previously but there's been no answer. Clicking theAUto Ttranslate" button results in "THERE WAS AN ERROR USING GOOGLE API. DETAILED ERROR = TRUE."

I have the Google API key. And, in fact, just adding a language, for example, French, results in the automatic translation of the Invitation and Reminder and Admin message elements. No need to even click the button. But Survey title, description, questions, etc. don't get translated and hitting the "Auto Translate" button results in the error.

...just adding a language, for example, French, results in the automatic translation of the Invitation and Reminder and Admin message elements.

This is because these are default text strings in the core language files. The other elements you mention are user-defined, so not in the language files.

I am not in a position to address the Google API error.