Hi there david n
Thanks for using QandA platform
I suggest you to activate the sandbox.
Selecting the Activate Sandbox button starts the activation process. If this is the first time you've activated a sandbox in Microsoft Learn, a second prompt asks you to accept the license terms. To accept the terms, you need to sign in with your Microsoft account, such as an Office 365 or Outlook.com account. If you don't have one.
try the below troubleshoots and hope they work
https://learn.microsoft.com/en-us/training/support/troubleshooting
https://learn.microsoft.com/en-us/azure/architecture/guide/azure-sandbox/azure-sandbox
If this helps kindly accept the answer thanks much.