504 Gateway Time-out

I recently tried logging in to my admin panel on my website and it didn’t work at all. This is a self hosted website with a domain bought from godaddy, and it has been working well all the way up to today. I really need help with this as soon as possible, and I have checked to make sure their is no problem with my wifi, DNS, or other errors on my part. Is there a reason why my website and the login panel for my website on www.remarpro.com is down?

The page I need help with: [log in to see the link]