I just discovered something.
When I load my flight on P3D with the FS Labs A32X and request boarding via the FS Labs MCDU (as usual), there is no "Number of passengers provided by addon" line in the log file and there is the "FSDT_GSX_NUMPASSENGERS is 0" line (see attached log 1).
Now, after requesting Boarding, I click on "Restart Couatl". I wait. Once Couatl has restarted, I request boarding again via the MCDU (as before). But this time I have the following lines:
FSDT_GSX_NUMPASSENGERS is 156
Number of passengers provided by addon is 156
(see attached log 2).
I've tried several times and it's the same every time. It doesn't work on the initial launch. But after a boarding request and a restart of Couatl, it recognizes the number of pax provided by FS Labs.
However, it doesn't work if I restart Couatl before a first boarding request.
Does this give you any clues or ideas?