If you are using , select the "Clean up" option to remove orphaned tickets, and use the "Show installed games" option to check if the Switch actually sees the DLC files as installed. Summary Checklist Potential Fix DLC doesn't appear in menu Reinstall DLC, Update Sigpatches "Corrupted Data" Message Update Sigpatches, Reinstall Game Content still missing Check Region Match (EUR/USA)
The game and DLC must be from the same region.
PC Building Simulator requires at least for the latest DLC.