Thanks for your question.
This looks like a sandbox issue itself, I tested same and saw same error. I will recommend you wait a bit or try in a free trial subscription.
Later you can try again with the steps below:
- Clear the cache and try to login to your Learn account using the proper credentials.
- Try using the incognito/private mode in your browser to rule out any cache or cookie issues.
See: https://learn.microsoft.com/en-us/training/support/troubleshooting
You can mark it 'Accept Answer' and 'Upvote' if this helped you
Regards,
Abiola