I have this problem since a few days. When I search my Wishlist I cant see many aircraft.
They practically load for ever and never show up. MS should be interested too because if I cant see aircraft on my wishlist i cant buy them unfortunately.
Make sure your logged into xbox and that DATA is on in settings.
AFAIK i always have to be logged in since I cant start the sim without being logged in. And why a few planes will be shown and the others not?
Data is on in the settings.
Update: As i guessed. I am also logged in in xbox too.
Just out o curiosity. Does there any support exist for MS resp. XBox Store? I am looking actually and I found the most stupid AI and a customer defense system which should prevent customers from asking questions like mine. Bad luck for MS since this will prevent me from buying products from them because I cant see what I bookmarked in their Wishlis 
THX but there is no information about my problem not it seems I can contact them. Probably they dont want to be disturbed.
Being Dec. 30th, knowing that many people (MS, Asobo, Moderators, users) are on vacation at this period of the year, it is understandable not having an answer right away. I am confident you’ll get support in the 1st days of 2024 once all are back from their deserved days off.
Sure but that they even dont offer an option to get in contact to describe my problem it least has nothing to do with vacations and tbh I am not sure if they really deserve vacations but that is something everybody could have his or her own opinion about it. And that problem is btw older too. I realized at first 2 or 3 weeks ago and thought they will fix it on their own. Probably they were on vacation too at the beginning of decembre. Who knows?
I am having the same problem. It started during the Beta for the current version. Items are not loaded properly and other items might show up twice in the wishlist. If I am changing the sorting I also noticed items appearing that are not in my wishlist anymore. So it might be some kind of caching problem that got introduced, when to sorting in the wishlist was fixed for SU14 (current version). The problems are happening for me on PC as well as XBox Series X.
There is a related topic in the SU14 Beta Archive.
https://forums.flightsimulator.com/t/marketplace-items-dont-load-properly-in-1-35-13/615159/5?u=rimcahiwao
Could you, as original creator of the topic, tag it as a BUG? It definitely is one.
Guess many have this bug. My solution is i dont spend money anymore there. It is obvious they dont want customers since this problem exist now for weeks. But we also should not wake them up or disturb them. Probably they are still on holidays and need some extra time 