NC11 + JavaScript XMPP Chat 3.0.2 - BOSH URL?

According to the Admin Documentation on GitHub i tried to install the app.

ejabberd works fine, i can connect with Pidgin.

I can open the ejabberd administration at https://localhost:5280/admin/ and the bosh url at https://localhost:5280/http-bind/ with Firefox.

I can’t connect to the BOSH url with the Nextcloud server

BOSH url with reverse proxy

http://localhost/http-bind/

gives me a status code 500 server error all the time

ProxyPreserveHost On
ProxyRequests     Off
ProxyPass         /http-bind/ https://localhost:5280/http-bind/
ProxyPassReverse  /http-bind/ https://localhost:5280/http-bind/

a2enmode proxy proxy_http
service apache2 restart