@c_schmitz, this is a rather serious issue since a customer just updated using COmfortUpdate to get rid of a different issue fixed at a newer release and now they can't access the plugin settings anymore.
Maybe you can include it at the next sprint so we can have a bugfix available next week?

I'm didn't remind when exactly it happen (but before 3.18) but to fix
master/admin/menus/sa/view => reset
/master/admin/menuentries/sa/view => reset

Capture d’écran du 2019-10-04 14-47-53.png (30,421 bytes)   

Capture d’écran du 2019-10-04 14-47-53.png (30,421 bytes)   

Capture d’écran du 2019-10-04 14-48-23.png (20,822 bytes)   

Capture d’écran du 2019-10-04 14-48-23.png (20,822 bytes)   

Thanks, Denis, that has indeed solved the problem!

It should still be fixed within the core because the mentioned work around leads to losing all menu adjustments.

I think i report it and add the way to add it manually …

https://github.com/LimeSurvey/LimeSurvey/commit/e78be38a0c36176ca7abf6acd00bff98135c6f19#diff-d3f0672bf165da530b05eb1bb3e491ce

maybe it's because "submenu" feature is disable between 3.17 and 3.18 ?

The fix by resetting the menus is easy enough and since it only seems a few select I am closing this issue.