A simple solution would be to temporarily rename all 41.296 airport files in MSFS.
Additionaly (to be on the safe side) adapt an F-104 livery to fit the Cessna 172 and copy that into a new read-only subfolder in your rolling cache. Piece of cake and works like a charm!
Jokes aside: I guess we’ll have to wait for SU9…
Thanks for the suggestion. I don’t have the rolling cache on either. Sadly, it still did not show any airports. I’ll reboot and see if that made a difference as you also recommended.
Releasing a pure sales tool that doesn’t work… at all… and then being fine with no sales from that sales tool until some next update is a bit funny… in an odd way.
Can’t figure these guys out
I have this problem also. The airports showed up the first time after I updated to SU8 but then vanished and the map is now blank every time I go in. Definitely not a Community folder issue as I have nothing in my community folder and never have.
I tried the suggested solution with clearing the rolling cache in the sim, no change, problem persists.
Me to: I always clear the rolling cache before and after each sim or world update. This time I did it twice.
Unfortunately this did not solve the marketplace map problem.
Yes, these are “strange times” 
Further development: If you open MSFS and just let it sit for about 1 hour or more, the airports show up in the map. Perhaps a slow download issue?
Ah, so this seems to be an issue with loading the data to populate the map?
Interesting find.
That’s what I discovered. I have not seen anyone else post the same discovery so I am not sure, at this point, whether it is the actual issue or just an aberration on my end. If it is related to load time, I expect download speed would make a difference.
Today, for the very first time, with no extra anything, the map populated with available airports along with my owned airports. The concept is awesome. Very handy to see what I have and don’t have, what’s on sale visually on a map. Nice touch that the airports on sale have a little “%” sign as an indicator.
EDIT
I leave to have lunch. Start the sim back up when I return. Blank map again. 
I wonder… are they going to make us vote to fix this? (Sarcastic rethorical question)
Sorry… posted to wrong thread 
That’s an interesting piece to the puzzle; I left it to load for an hour, and then eventually got a “you’re offline and can’t connect to the marketplace message” after which I got kicked out of the marketplace. Funny enough, I never lost connection to the internet the whole time.
I think your theory might be right; this might be a loading issue from the server, rather than a client display issue.
Definitely an interesting hint, re. leaving it for a while. I’ve only ever seen the map populated once, and that was in fact when I had launched the sim only to leave for a loooong coffee - on return, I went to the map and saw it populated! Before that, and on every launch since, blank map.
Same for me . Nothing showing.
Hey… Microsoft fixed the problem for me. I was on the runway of KBID in a King Air when the sim crashed to the desktop. When I rebooted and came back in all the airports in the marketplace were showing up on the map again. Strange fix (smile), wonder how long it will last?
Next day… all gone again (sigh!)
I know they don’t usually do patches and fixes anymore with World Updates, but I was secretly hoping they would at least fix this super glaring thing in todays World Update 8.
They introduced this map thing in the last sim update, and it has never worked for me. Not once.
Now it looks they really are going to let us wait till they possibly maybe hopefully address this in the next sim update (which currently doesn’t even a release date) huh?
Loading the game in safe mode worked for me but as soon as I load in normal mode the maps bland again
I just had it working today, second time since the update. I thought, ok, they must have done something…stupid me…wrong. Shut it down and restarted it and no airports. Idk. Lol. M and A…you had me there for a minute. You gotta laugh. It’s becoming a joke.
On my set up, removing AIG “aig-aitraffic-oci-beta” folder from the Community folder allows the airports to appear on the marketplace world map immediately on launch of MSFS. If this folder is present then I do not see on launch the marketplace airports on the relevant map.
I have not tested if the airports will eventually appear if I just leave it for a while.