Fortunately, there are a few potential fixes that players can try to resolve the NSP DLC update issue:
Assuming you have a modded Switch (Atmosphere) and a USB cable or FTP setup: pc building simulator switch nsp dlc update fix
For users using custom firmware (Atmosphere, SX OS, or Ryujinx/Yuzu emulators), the entry point is the (Nintendo Submission Package) or XCI (Cartridge Image). Here is the current status as of 2025. Fortunately, there are a few potential fixes that