Snap install after setting up certbot: Have I blundered?

I set up an Ubuntu 16.04 machine, and installed and ran certbot to obtain a letsencrypt certificate before I installed Nextcloud snap. Now I can reach my ‘Apache It works!’ page, but there’s no sign of Nextcloud. I’ve tried localhost/nextcloud, and 192.168.X.X/nextcloud and have also appended both http:// and https:// to those addresses.
I have a horrible feeling I’ve blundered. Is there anything I can do, or do I have to go back to the beginning?