DeepL API Authentication failed.

[Alkaid-C]

Environment:
Plug-in version 2.8.2 (in the Firefox store)
Firefox is 120.0.1 (64-bit), Windows 10
DeepL Pro API

What happened?
After I set the DeepL API key, when I try to translate, it shows:
Error: Authentication of DeepL API failed. Please set the authentication key and plan correctly on the settings page.
I double-checked, and I am sure my API key is correct.

What I tried?
I tried to reset my API key in the DeepL panel; restart the browser many times; and change the API plan to free/pro. They didn't fix the problem.
Though after switching to google it works.

[Alkaid-C]

I tried the same thing on Microsoft Edge version 119.0.2151.97. It doesn't work also.

[Vojtak42]

You have to delete ":fx" at the end of the key. And translating through the button on the page will start working but on the other hand translating from this windows will stop working:

[Gregory108]

Similar problem. No cue and no clue how to solve it.

Plugin version 2.8.2
Firefox 125.0.1 (64-bit), Windows 11

Uninstall and install again solved the problem. I did not even have to delete :fx suffix.