How can I categorize expenses in the app? My vendor list is empty but only on the transactions page. This used to work fine but it's been a few weeks since it emptied.

If I go to vendors shortcuts, all my vendors are listed. But when I try to categorize bank transactions, I have no vendors at all. This is only on the app, not the computer. I've been using the app to categorize transactions for over a year, but suddenly, a couple of weeks ago, I don't have any vendors anymore.