[...]Clearly the issue is your assets are not in the right directory as expected of RetroArch for whatever reason, which is why nothing loads in your menu. Chalk it up to misplacing of asset folders, or an old/outdated configuration file, I won't judge.
The only suggestions I can make to you are these:
1) Check your directory settings in
Settings -> Directory; does "Assets" point to the proper folder as shown below?
2) Check the assets folder on your filesystem (either through VitaShell, FTP client, or as a storage device on your computer); does it look exactly as shown here with the same directory listing?
(And while you're at it, make sure that the
3) If all else fails, then go to
ux0:data/retroarch, delete
retroarch.cfg, and triple/quadruple check that your assets are in the right subfolder
(taking care to ensure that the XMB/glui folders are in the assets subfolder, as the format demands).