If you have a HP printer/scanner that relies on the HP MFP Scan application to scan (sometimes, there is no other way), the app may fail to run on Windows 11. Here is how to fix it.
Run an elevated command prompt, and enter the following commands:
c:\windows\SysWOW64\regsvr32.exe "C:\Program Files (x86)\Common Files\HP Scan Process Machine\ScanProcessMachine.dll"
c:\windows\SysWOW64\regsvr32.exe "C:\Program Files (x86)\Common Files\HP Scan Process Machine\ImageEngineManager.dll"
The application should be able to run and detect the scanner. Doing a fresh install with the latest driver now seems to also fix the problem. Either way.