Download the latest firmware (currently version 3.74) from the Official PlayStation Support Page Emulator/Legacy Files: If you are using the Vita3K emulator
Put your PS Vita into to prevent it from pinging Sony's live servers. Connect the Vita to your PC via the USB cable. Open the Settings app on your Vita. Go to System Update > Update by Connecting to a PC . Psp2updat.pup Download
This often means the file was not downloaded completely or the transfer was interrupted. Re-download the file and try again. Download the latest firmware (currently version 3