I suspect that this error occurred due to a previously used API key, and somehow, even though the API keys are inactive, Cursor seems to recognize them as active. You can try reinstalling Cursor to see if that fixes the issue. You need to delete one folder. You can also just rename it. A new one will be created upon reinstallation, and if needed, you can restore the folder to bring back your previous Cursor settings.
You need to delete the folder at these paths:
Windows: %APPDATA%\Cursor\
macOS: ~/Library/Application Support/Cursor/
Linux: ~/.config/Cursor/