I have been unable to login to the admin page of a developed wordpress site. Im presented with a 504 gateway error. I can get to the admin log in page, after entering the correct details it gives me timeout. I now can not log in to edit the page. However the site is still accessible like normal from the usual domain with no errors present. Could it be a plugin preventing this even though nothing has been changed in the dashboard for a few months?
This usually means the server is timing out before the processing of scripts completes. Try to increase the memory limit and maximum execution time.
Try to increase it as much as you can. Start with 256MB of memory and 120 for execution time. If that doesn't work just gradually increase both values.