I don't use their plugin.
I use the XPUIPC plugin instead, and I have had no problems.
EDIT: Found a link for you ............... https://forum.fsairlines.net/viewtopic.php?t=9287
Edit 2 - Link changed to a later version 2.0.5.9
BTW if you do use XPUIPC, once you have copied the plugin into XP11, open the XPUIPC.ini file in a text editor and change your local network IP address from 127.0.0.1 to your actual network IP. In my case that is :-
[XPUIPC SETTINGS]
Tune value = 00
Server Address = 192.168.1.3