I had a PM from Shogun who was testing the new release that two theatres were working offline, but not online.
For some time our EAW series has allowed host only missions to be played in multiplayer- other exes need a minimum of two players. So if you fly host only then you are the host. This may sound obvious, but it is critical to the discussion.
There are settings in the host's ini file for target, bases and aircraft. You can see mine overlaid on the DSP here:
What I think happened is that we had been playing the crazy set-up as a test. It uses the ETO target set with more than 300 targets. Then Shogun had probably switched to a theatre with fewer targets and bases.
If you switch to another theatre when flying online then the current target and base values stored in your ini file may refer to targets and bases that do not exist in the new theatre. This does not affect offline play, but causes a CTD online.
This problem is the reason for the panel on the right of the DSP which allows the host to select a theatre, and a file that modifies his ini file with values for that theatre. When I did that I was able to fly WW1 and the new Mediterranean theatres host only.
An emergency fallback is the "ZERO" folder and its single file. Choosing this sets all the base, target ans planes value to zero, and is guaranteed to work. However, you then need to know the values to set on the multiplayer screen and there is no map available at that stage.
If you want to be even more adventurous as a host then you can use the "MPU2016.exe" to make and save new settings
If circumstances arise that are likely to fly as the host then it is worth learning to use this software.
Please note that in the very latest set-up with all the 'planes' folders moved to the "Aircraft_Inventory" folder there is a CTD when you select a planeset. This is happening because the paths listed in the "PDir.set" and "FMDir.set" files in the "Theatres" folder refer to the original 'planes' folders which were in the root folder.
I am about to fix that.
I have mentioned this before, but we really need to make a library of these files for online hosts to use. As far as I know the only ones we have are the ones that I have made.