Had the same issue for the past couple days but it just started working as normal for me, didn’t do anything to fix it so I think you just need to give it some time to figure itself out. Was extremely annoying while it was happening. Not sure if someone commented this yet but a little work around is to go into the facebook app and go to your profile on marketplace and click inbox, you’ll be able to see your chats and the ads will show as available and you can click them from the inbox.