"Your installed version of Advanced Module...

- I have a Joomla 3.10.6-site.
- I've updated there AMM to version 9.0.4.
- Afterwards I ran a migration of Joomla to version 4.1.0.
- Afterwards I get these alerts in backend:- When I go to Extensions > Manage and try to enable "System - Regular Labs - Advanced Module Manager V9.0.4" I get the same messages and plugin is disabled.
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- On a test site with Joomla 4.1.1-dev I updated from AMM 9.0.0 to 9.0.4 via Extensions > Updates.
- Nearly same behavior. Plugin is disabled afterwards with related alert.

I'm nearly sure that this site never was a Joomla 3.
I've reinstalled already AMM on Joomla 4 (several times 😉 ).

I'll try now an uninstall of all regular labs extensions and then a new installation. And hope that not all settings will be lost then. Let's see.

In both cases just uninstallation and new installation helped. But it works now on both sites and all settings are still present. So, OK for me for Joomla migrations.

As far as I remember I posted here in another(!) issue where I also had to go the same steps before V9.0.3 worked then. That was a blank installation of Joomla 4.

At the moment I don't have an installation where I can invite you if that was meant in your last post.

Nope! File permissions and other things are correct. It's a standard account at All-Inkl.