(1) TAC, that might have been a slip, try maintenance as 1 (I'll look in a moment at one).
NOT-MAINTENANCE IS 0 AND MAINTENANCE IS 1. In phpMyAdmin just go to the table named setting (there may be a prefix like oc_) and then find the record (row) for config_maintenance, then in the value field (column, usually right side) find the cell where they intersect (field x record, column x row), and in that cell edit the 0 to 1.
(2) Back up database(s) now, using phpMyAdmin / Export. Before (3).
(3) As for getting in, remember (you've seen it before) ocreset.php, there is no mail, admin pass is reset on the spot. Download at
http://www.jaygilford.com/download/ocreset but first read instructions at
http://forum.opencart.com/viewtopic.php?t=15626. Be certain to delete it afterward.
(4) Your OP link goes to an edit page, difficult to navigate. You evidently mean your
http://forum.opencart.com/viewtopic.php ... 15#p474484 in his
http://forum.opencart.com/viewtopic.php ... 15#p472487.
(5) Those problems owe to server or hacker. You already long since turned off error reporting (to screen), in more than one OC. Several of different vintages went inexplicably bonkers, inexplicably at once, without your having helped. There may have been a php.exe, Plesk, phpMyAdmin, or mysql upgrade done. Support is obviously not being either straight or helpful. If you look at your host's own landing or inside Plesk you should find a URL for server status. If the server was down or being upgraded, explanations will be very short. Since they are coming back one by one, odds shift toward the host being responsible, but you won't rule out hacking without seeing it in ftp and Plesk.
Note
http://forum.opencart.com/viewtopic.php ... 64#p474764 . . .