Thank you for reaching out to us on the Microsoft Q&A forum.
I understand the frustration you're experiencing with the sandbox provisioning issue. It can be quite disruptive to the learning process.
Based on the information you've provided, it seems that you may have reached your daily sandbox quota. Microsoft Learn imposes these limits to manage resources efficiently and ensure fair access for all users.
It seems you have reached this limit. I recommend waiting for 24 hours before attempting to provision a new sandbox. After this period, you should be able to use the sandbox again without any issues.
If you need to continue working within the 24-hour period, you could try using a different Microsoft account to provision a new sandbox.
If you have further and issue, please don't hesitate to reach out to us if you have any further queries. I hope the information provided has been helpful to you! If so, please accept the answer by clicking the Accept Answer / Upvote on the post. We value your feedback, and it will help to assist others who might have a similar query. Thank you for your contribution in enhancing Microsoft Q&A!