Try the following basic steps first:
- Use a different browser and try incognito mode
- Go to: https://learn.microsoft.com
- Clear cache and cookies
- Sign in with only one Microsoft account
If that does not work, Please check this workaround by TP as I see it solved the issue on a similar issue.**
https://learn.microsoft.com/en-us/answers/questions/2239116/unable-to-use-microsoft-learn-sandbox-continuous-s?comment=answer-2016352&page=1#comment-1986790
You can mark it 'Accept Answer' and 'Upvote' if this helped you**
Regards,
Abiola