Disassemble the PSP, clean the button contacts and hardware, and re-assemble. If this does not fix the problem, you probably have an issue with the actual hardware itself, instead of just dirt and grime. In which case, you will need to find an after-market online retailer of PSP replacement parts, and order a new faceplate and buttons, then (as mentioned above) disassemble the PSP, install your new parts, and try again... If you want to be very thorough, also replace the rubber contact sheets that the buttons press down on... They should be available through the same retailers.
Hope this has helped, and you have a great day.
Hope this has helped, and you have a great day.
