Hi John Freeman,
Thank you for reaching out to us via the Microsoft Q&A forum.
We regret to learn of the issues you are encountering while attempting to activate the sandbox.
In response to the error message provided, please adhere to the recommended quick fix outlined in the troubleshooting guidance page, as depicted below:
Additionally, to address this matter, kindly follow the troubleshooting steps outlined below:
Step 1: Sign out from all tabs within your current browser and clear the cache files. Subsequently, attempt to log in again using your Learn ID credentials.
Step 2: Sign out of your current browser session and try to log in using an incognito window or private browsing mode.
Step 3: Switch to an alternative browser and try to log in once more.
Step 4: Attempt to log in with a new personal Microsoft email account into the learn path using a completely different browser. Should you not possess one, kindly create a new free Microsoft account. Note that a Microsoft account, such as Office 365 or Outlook.com, is required for sandbox access.
Step 5: If access to the sandbox remains unattainable, we recommend registering for an Azure free account through the provided link: https://azure.microsoft.com/en-us/free and establishing a sandbox environment there.
For guidance on executing Microsoft Learn training exercises within your own subscription, kindly refer to the following link:
https://learn.microsoft.com/en-us/training/support/use-your-own-subscription
Should you find this information beneficial, kindly indicate your acknowledgment by clicking the "Upvote" and "Accept Answer" buttons on the post.