Well, no one offered any help 
But I figured it out myself.
Seeing as there are literally hundreds of threads about this issue online it seems like I’m not the only one who has got caught up on this.
[SOLUTION] You just need to grant httpd/apache outbound network access via SELINUX.
setsebool -P httpd_can_network_connect 1
That’s it.
I would strongly suggest the NextCloud team add this to the administrator documents as it’s not present in the setup guide or admin guides anywhere.
Cheers.