I had a similar issue where i was unable to contact tower last week 3 times in a row, back to back, every time i reached my destination, i would be unable to get through to the tower freq. So in those cases i would divert because ATC was active and with inbound traffic. After leaving the airspace i would turn back again towards the airport and then I’d be able to contact tower again.
I made my own support thread about the issue, and got tips from other memebers but i still don’t know what caused the issue? Either way, i don’t have the issue anymore after the recent update 18.4 and what Daniel suggested would not work for me at that moment because i couldn’t see tower as active, being green. And this would happen when I’m being handed over from APPR to Tower or I’m on Unicom and Tower comes in, but i can’t see them or contact them, so i would divert. Happened only 3 times consecutively and then, no more issues… 😶
If you ever happen to not be able to contact the tower freq and can’t get to them via the map either then try leaving the airspace and return once you’re 40 to 50nm out. It worked for me and kinds resolved the whole issue wierd enough… 🤔
But this was when ATC was active… now with 18.4 a new issue gas arised which is what the OP is talking about.
Yesterday when i was inbound at KDEN, i couldn’t find KDEN Unicom on the list scrolling through all the airfields i didn’t see KDEN. Until I’m short final and it pops up, i quickly announce Final RWY XX and land safe as no one was on the runway. But it was wierd as why i was unable to find KDEN on the list for so long, but on my return flight to EDDF i found the Unicom for that airport right away from a much further distance…?