I tried to open the menu several times. Each attempt was recorded in the log but nothing in the log explains why the menu didn't display?
As I've said, it was likely because the airport cache was still rebuilding because if it was, it's 100% sure you'll cause the menu to be stuck, if you call it multiple times in a row.
I had no indication SimConnect had ceased to run.
That's was just an assumption. Of course, if you restarted couatl manually...of course it restarted but again, that's not the main issue, the main issue is why it regenerated a cache for a restart during the middle of a session, where the scenery library surely couldn't possibly change.
Unless, you said "I restarted couatl", but if what you really did was restart couatl with the rebuild the airport cache option, in that case it's normal it's regenerating the cache, because that's what you asked it to do.
So, again, it's all normal, and the only problem was trying to open the menu several times in a row without waiting for EVERYTHING to be ready.
"EVERYTHING", after such restart means:
- the airport cache should be complete
- the model cache should be complete
- if the scenery has custom GSX jetways, you must wait for ALL of them to be created ( not just the ones in front of you ) before you can use the menu. This is always valid, even without the "restart and rebuild cache option"
In addition to that, in P3D5, there's an extra delay added by the html menu the first time you call it ( = after a restart ) so, the key has been received, the menu IS being created, but it take a couple of extra seconds which might mislead you thinking GSX is not working, but it is, and it's just the first extra slower call of the menu in action. Same as above, if you press the key again
while the menu is being built, you surely cause a menu stuck, since we have no way to detect that situation.