Last month’s Sims 4 patch broke custom content chairs. Fortunately, Sims 4 Studio has now released
The batch fix will repair all broken chairs so Sims will sit at them if they’re placed by a table or desk. Using this batch fix will cause all fixed chairs to disappear from your saved games. They will be available in the catalog, but they won’t be in Sim homes where you placed them. This batch fix will also be added to the Batch Fix History (present in the Warehouse view) in the .package.
There’s also an experimental new feature added that modifies your save game to swap out broken chairs with the’r batch-fixed versions.