Problem with 'mode' button

Hi wondered if anyone could help.
I just bought an MPC 500 second hand from E-bay, and am trying to follow step-by-step instructions in the manual. I cant seem to access the menu screens when I press the 'Mode' button. Is there something I'm missing, or should the menu's appear as soon as I press it?

Could it be a dodgy button, or is there a 'Knack' to it?

So to be clear... pressing mode and then a pad, doesn't change you to that mode?

It is completely possible you have either a bad tact switch or the plastic button is messed up.

Might be worth taking the cover off and just have a look to see if everything is seated properly.

Yes, that's correct, nothing happens when I press 'mode' then another function/pad, and discovered none of the buttons on that row are working either!!

I have taken the cover off as you suggested, taken the white plastic connector off and then on again, but still doesn't work...... might be a job for the repairman, as I'm not keen on the idea of pulling the whole thing apart!

Thanks for confirming it wasn't just me missing something.