@cas MantisBT and most of the plugins come with a license agreement. Everything is Ok, as long as you do just what is allowed by the license. E.g. MantisBT Core comes with a GPL license https://www.mantisbt.org/docs/master/en-US/Admin_Guide/html-desktop/#admin.about.license https://www.gnu.org/licen...
You should try latest 2.26.1
E. g. there are better checks and messages for the database driver that is missed on your system, see https://mantisbt.org/bugs/view.php?id=33519
Select the affected project in the projet selection drop down and goto page Manage > Configuration > Workflow tresholds.
Provide a screen shot of that page.
Version 2.26 will be the last release supporting PHP 7.2 and PHP 7.3.
Starting with MantisBT 2.27.0, the minimum PHP version will be 7.4.
See also this issue.
I thought you used it based on the question from cas did you check the advanced filter options? Click in the top right corner (of the view all bugs age) next to the chevron... and I did use that advanced filtering functionality but it does not solve my problem. If it works the way you expect in UI, ...