Hi willowpape welcome to the forum.
If you have any mods or CC in your game take them out and try the selling scenario again. If it works you'll know it is a mod problem or a broken piece of cc.
I can't find any specific bug report on this so if it isn't related to mods it may well be something new that has occurred since the toddler patch.
Have you tried deleteing the localthumbcache.package file from your TheSims 4 folder? Or perhaps a
Factory Reset (click) if nothing else is helping?
Check that the sims have access to the object, if items have been place with the MOO cheat this might be causing issues.
You could also try saving your retail shop to your library, bulldozing the current one and then replacing it, but this will reset perk points, I think from memory.