I have Nextcloud 18.0.4 installed on Ubuntu 18.04 as a snap, with nginx as a SSL proxy, and forwarding it unencrypted to localhost:81. I can login fine from the web, but when I try to connect the iOS app, it says
Error
It is not possible to connect to the server at this time.
forbidden
The web login method doesn’t work because the Log in/Grant access (app token method) button simply doesn’t work.
I ran nextcloud.occ log:tail but no new log errors came up. I have no idea how to troubleshoot this.