You are trying to install an incremental update (like SP21 v4.5) on a completely clean game or an outdated patch version (like v3).
SmokePatch installers use different execution methods depending on whether you own the official Steam game or a non-original copy. Choosing the wrong option during setup breaks file mapping. cannot update the patch sp21 v4 was not found in the updated
Right-click the update .exe file and select Run as administrator to grant it full system read/write privileges. You are trying to install an incremental update