while trying to download the file through the Adrenaline app? Adrenaline - Vita Hacks Guide
Launch Adrenaline again. It should now detect the file and prompt you to install the firmware by pressing Troubleshooting Error ux0:app/PSPEMUCFW/661.PBP: download 661.pbp
If your PS Vita is connected to the internet, Adrenaline can typically download this file automatically when you first open the app and press Manual Download: while trying to download the file through the Adrenaline app
Ensure you do not overwrite existing critical files in that folder during transfer. Finalize Setup: download 661.pbp