I'm runnig Jlex Review 6.0.1 on J 3.10.12. I am in the process of troupbleshooting upgrading J3.x to J 4.4.1. Updating crashes, so I had to disable almost all plugins, update, and then painstakingly go through re-enabling one at a time. Re-enabling "System - Jlex Review" results in "Call to undefined method Joomla\CMS\Application\AdministratorApplication::isAdmin()", which is the same error I get when attempting to update without disabling almost all plugins first. It seems this JLex Review plugin is my upgrade blocker.

No further administration is possible after the error. I have to blow away the staging site and start again.

I tried re-installing Jlex Review 6.0.1 onto J 4.4.1 prior to re-enabling the Jlex Review - System plugin to see if it would help, but it did not. The same error persists.

See attached.