Settings page not found / Upload impossible

Hello to Support..

We use WP and BP in a multisite….we need group documents in BP on Main Site of Multisite….

Plugin installed, Activated, “Documents” Tab availible like supposed to be…

Problem:

Upload throwes Error “This file type is not supported”

Trying to enter the settings page via Plugin Details trys to open the page via:

https://ljv-sachsen-anhalt.de/wp-admin/settings.php?page=bp-group-documents-settings

throws this: The requested URL was not found on this server.

Also “Buddypress Group Documents” doesnt show up under Tools sektion of WP menu….

Any ideas? What is the problem? Kown issue on multisite?

I got the plugin running flawless on same WP Template just as a single site…

Thanks for Support!