Are you playing this on the Itch app (downloaded version) or the web? Did it happen right away or after a couple of in game days of playing?
Also, you might be able to afford the plant but if you switch to another pot it will be more expensive. The base price is in the terracotta pot.
i have it downloaded through the downloaded app onto windows.
If you go back to your save, does it still not work? We haven't seen this bug before so any details really help us---we also have a pretty big update coming out in the next week so that might take of this issue!