Hi! If you're like me and use Nextcloud through a reverse proxy, sometimes it will just act dumb and refuse to log in to apps, either opening a pop-up that says something along the lines of "Strict mode: no HTTP allowed!", or just hangs on a spinning animation.
That's because it thinks you're using HTTP to access it, when your reverse proxy is actually securing it.
That's why you need to set a config parameter to make it use HTTPS for links, even though it thinks it's serving over HTTP.
If you use NixOS, like I do, then that option is
services.nextcloud.config.overwriteProtocol = "https";. In the
regular nextcloud config.php, that option is just
overwriteprotocol = "https";.
I hope this handcrafted page helped you!