#2 Nov 29, 2017 01:48
I've had this problem a number of times with various fixes, and I had the same yesterday and reinstalled 6.9.3 for now as I'm too busy to chase this up.
It seems that something stops the php files from being read, you can see if you can access [install/index.htm] and [install/test] - which has a deafult htm index file.
Do you have ftp access? cpanel access? Remove [/config/umaintenance.php]
Download a fresh copy of 6.9.3 and ftp ?