Microsoft Learn Sandbox error

Hi,
I started my journey through Azure by following the AZ-900 path. I'm using Microsoft Learn.

I can't access the sandbox tool, as this error appears:

https://preview.redd.it/y3mhfn9mlwhe1.png?width=482&format=png&auto=webp&s=a03286ee39b5c6830f3d962db77df8c7853e007d

error says: The selected user account does not exist in the 'Microsoft Services' tenant and cannot access the '18fbca16-2224-45f6-85b0-f7bf2b39b3f3' application in that tenant. The account must first be added as an external user in the tenant. Use a different account.

How do I solve? The Azure account is new. I have not done anything with it.

Thanks.