Issue summary:
Based on your post, you are having issues at the moment to launch Sandbox session for Azure. We are more than happy to assist you with this inquiry!
Recommended solution:
For you to get a better support for the inquiry we are going to direct you to the correct support Microsoft Learn support - Troubleshooting known issues | Microsoft Learn because the description of your case, is directly related with your Learning account and not with your Microsoft’s Certification Profile.
Please go to the link and select the option problems with the Sandbox
At the same time, we recommend you contact the Microsoft Azure Support via this link Azure Support Options | Microsoft Azure, since they handle all the requests related to the Azure Certifications, we can assure you they will provide you with specialized assistance and accurate answers to your inquiry.
If you need more information about Sandbox activation, go to: Microsoft Learn frequently asked questions (FAQs)