@SimUser1981 Are you using any mods to run the restaurant (or mods in general), or the bistro store set? Try changing the lot type to something other than cafeteria. Certain lot types can be finicky to work with, whether or not mods are involved.
If it's not helping, use "save as" to rename the save, so you have a backup copy to experiment on. Then quit to desktop and delete the five cache files in your TS3 game folder in Documents. They should be deleted regularly anyway, and while you're troubleshooting, every time you quit. For reference, they are:
- CASPartCache.package
- compositorCache.package
- scriptCache.package
- simCompositorCache.package
- socialCache.package
Reload the renamed version (i.e. your backup), have your sim sell the restaurant if it's owned, go to Edit Town, save the restaurant to the bin, bulldoze the lot, change its lot type to residential and then to a different commercial designation, then quit and delete your cache files. Then reload, place the bin copy of the restaurant, and test. This is more thorough than just changing the lot type on the fly, which might not work correctly even if you pick the correct designation. But once you know what lot type you need to use, you can apply it in your main save without having wasted all that in-game time testing.