502 bad gateway error - ubuntu snaps

I havent used my rocket.chat server in a month or so. It is running on a vps.
I attempted to browse it via desktop pc app and the app opens then immediately shuts again in windows 10.
I then opened web browser and enterred https:host.domain.com and it throws

502 bad gateway error.

I have a complete mental blank now. Am i trying to access the rocket chat server wrong?

I can still SSH into it using putty. So how do i fix this?

  1. what url should i be using to access rocket.chat server from web browser?(how do i find this from putty)
  2. if something else is wrong, how do i fix it?

ah hang on…making progress. If i change url to http://host.domain.com:3000 (no ssl and also include port, i get to a login screen).

Why cant i use https to initiate the handshake in web browser? (it redirects to https no problem if i first use http)