Hi @adil ,
This may be a problem with the database. If you want to view the SQL Server error logs, the default path is C:\Program Files\Microsoft SQL Server\110\Setup Bootstrap\Log. If you are not very familiar, please contact the database administrator to confirm whether the database is in a upgrade. And the Windows event viewer is also a way to see if there are other error messages. Here are some information about it:
https://www.howtogeek.com/123646/htg-explains-what-the-windows-event-viewer-is-and-how-you-can-use-it/
By default, all SharePoint errors are logged in a folder called Logs which is located in the path C:\Program Files\Common Files\microsoft shared\Web Server Extensions\15\LOGS.
Here are some similar threads for your reference:
https://blog.sqlauthority.com/2019/05/20/sql-server-fix-error-login-failed-for-user-reason-server-is-in-script-upgrade-mode-only-administrator-can-connect-at-this-time-microsoft-sql-server-error-18401/
https://www.wikitechy.com/fix-error/fix-error-server-is-in-script-upgrade-mode-only-administrator-can-connect-at-this-time
Best regards,
Elsie Lu
If the answer is helpful, please click "Accept Answer" and upvote it.
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.