Most homebrew plugins (like SD2Vita drivers) are optimized for 3.65.
Download the official PSP2UPDAT.PUP file for region-specific 3.74 firmware from trusted PlayStation documentation mirrors.
Follow the on-screen prompts to download and install the 3.74 firmware. Method 2: Update Via a PlayStation 3 Console
: You must generate a "Device Setup Password" via your Sony account settings online to log in on the Vita.