Cannot not reach instance

When I try to connect Nextcloud to xWiki and add the instance it says:
"Could not reach this instance"
Interesting enough, in my user settings I can try to connect my account to xWiki and the redirect works but then says "Host violates access rules"

At the first attempt I get a dialog from xWiki asking for permissions. I click allow and from there on it just says "host violates access rules"

Both xwiki and nextcloud are using https

Am I missing something?