We just applied the 5.2.6 FortiManager upgrade. We're coming from 5.2.4. After the upgrade, the login page shows the usual "The system is unavailable due to configuration update. Device logs are not accepted at this time." and the progress bar is stuck at 75% for the past 10 minutes or so. Is this expected? I haven't had an update take this long before.
in 5.2.6, there has some code added for upgrade check and fix for the db issue if any during upgrade, but the detailed info only printed on console during upgrade
if you still see the issue and GUI stopped there, you may need to open a ticket and provide your 5.2.4 db, send me the ticket ID and I will follow up your ticket