Without error information it’s difficult to find the cause of failure if any. May I please know what’s the region of your server is hosted?
And if you haven't already, please attempt the upgrade using the CLI and share the error details if it fails.
Here is the steps and document for reference.
Perform a Planned major version upgrade from MySQL 5.7 to MySQL 8.0 using the Azure CLI
Also request you to check below Prerequisites before proceeding with upgradation
· Read Replicas with MySQL version 5.7 should be upgraded before Primary Server for replication to be compatible between different MySQL versions, read more on Replication Compatibility between MySQL versions.
· Before you upgrade your production servers, we strongly recommend you use the official Oracle MySQL Upgrade checker tool to test your database schema compatibility and perform necessary regression test to verify application compatibility with features removed/deprecated in the new MySQL version.
· Trigger on-demand backup before you perform major version upgrade on your production server, which can be used to rollback to version 5.7 from the full on-demand backup taken.
Let us know if you have any questions or need additional information.
Thank you!