XF 1.5 Down For Maintenance?

Aloha. I've been experiencing difficulties with loading the site for a couple of days. Thought it may have been my pc, but this morning members are complaining of getting updates hours late, can't send pm's, getting alerts for conversations and threads that do not exist, etc. Also, none of the administrators can access the admin panel.
"Internal Server Error" has been popping up off and on since last night. Now I have an "Internal Server Error" alert saying that the server is down for maintenance.
Not to be a dummy, but I just want to be sure that I am having a server problem and not a host problem. As I have experienced similar problems in the past, and it turned out to be a problem on the host end, and not with Xenforo. I put in a support ticket earlier this morning, but have not heard back as of yet...

Please advise if possible.

Mahalo for your help.

Error Service unavailable- Server Down for Maintenance 2-19-2017.png