CONTACTS menu not visible / no access to contacts

Nextcloud version: 17.0.1
Operating system and version: OpenSuse Leap 15.1
Apache 2.4.33
PHP 7.1

CONTACTS 3.1.6

As an admin, I’ve created an NC user belonging to a user group., let’s say “GroupA”

When this user logs in, “contacts” menu is hidden, and a manual access to https://example.com/index.php/apps/contacts is redirected back to “files”.

WHY???

If add this user adittionaly to a second group, where I know that these users HAVE access to “contacts”, and have been able to create addressbooks etc., this user gets “access” to “contacts”.
As soon as I remove him from that group, again no access to “contacts”

Any hints?

Thanks,
Michael

SOLVED:

Found in “Apps” menu:
When clicking on “contacts” app, “Limit to group” is set for some groups.

Good to know !

(But no idea how, when and why this was set. I’m the only admin, private use, and I’ve for sure never added groups here. Looked also for “calendar”: checkbox for “Limit to groups” set, but no groups added there. Guess it’s some “upgrade relict”, this NC instance has started LONG, LONG ago as an Owncloud instance…)