One way to move forward would be to add this line near the top of your wp-config.php file (in the root of the directory where wordpress is installed):
error_reporting(E_ALL); ini_set('display_errors', 1),
right underneath the “<?php” line which should be at the very top.
Then, farther down the file, look for lines beginning with “define(“, then add one that says
That’ll force wordpress to do debugging/error reporting basically before anything else loads and print it at the top of the page, and from that error report you might be able to google around for an answer online. Then, to turn it off, you can just comment out or delete those lines and save them until it breaks again.
I guess that only works if you have access to that file, but I think you ought to through your ftp.
Hope that’s helpful! For more info you could always google on “wordpress admin blank screen of death.”