Pioneer DEH 6700 MP buttons not working

Depends if the problem is with the face plate or the unit do you have someone with the same stereo that you can try otherwise you need t get it in to a service centre

Try cleaning the connections from face plate and on unit itself with a pencil eraser.

try using a qtip and rubbing alcohol or a pencil eraser to clean the contacts of the face and subpanel.

go to pioneerelectronics.com and there you can download a copy

pull your face plate completely off, look for a small indented hole that you can fit the tip of a pen in. note(its not on the back of the face plate) on the actual head unit. make sure while doing this that your vehicle is started or at least in acc position

theres a spring loaded device behind face plate used to kick face out either the spring broke or became un seated

if all you need to do is get the cd out there is a small hole in the foront of the unit just big enoufe for a papper clip just stratien one out and put it in the hole but if you want to fix your unit then you will have to take the face plate apart get the soda out of the face plate i always use glass cleaner and cotton swabs for this just make shure you get any and all residue off before you put it back togethr and make shure you clean the rubber pads under the buttons and you should be good to go

An install gone bad. Something is hindering free movement of the face plate open mechanism. Closely inspect the top edge of the bezel, is the face plate trim ( thin plastic ornamental frame covering the ugly aluminium mounting sleeve) snapped securely back in place? has it been fitted upside down?, is it deformed?.

try taken face plate off if detachable then put back on sounds like the face plate clip might be weak and or missing spring inside
but if face plate stays attached just need to clean and put back on right to deck no easy way to say that

it needs a flexible pcb (the one that connects the face to the main board) it's a common fault on these units, you see every time you power the radio the fascia rotates and therefore flexes the connector and after time the pcb starts to break some of the connectors. If you feel confident enough the flexible pcb's are not too difficult to replace if you can get a replacement.