Your Vita doesn't see the PSVUPDAT.PUP. Solution: Ensure the file structure is exact: PS Vita/UPDATE/PSVUPDAT.PUP (all caps for the file name). The folder names are case-sensitive.
If you want custom firmware (Adrenaline for PSP, RetroArch, VitaDB, overclocking, SD2Vita, game backups, etc.), . Why?
. While it was the fourth update released in 2019, it introduced very few visible changes, primarily focusing on minor text modifications in error messages. Official Installation and Download