include('mantis_offline.php') [line 34]
Before doing anything... check if MantisBT is down for maintenance
To make MantisBT 'offline' simply create a file called 'mantis_offline.php' in the MantisBT root directory. Users are redirected to that file if it exists. If you have to test MantisBT while it's offline, add the parameter 'mbadmin=1' to the URL.