Hello DSC security system experts 

I have a fully working DSC 832 system with an old LED keypad. Wanted to upgrade to a nicer LCD so bought a second hand PK5500. When I connect it parallel to the original keypad it lights up and displays "5 restaurant unavailable" and nothing more happens. It does not respond to any key input, *8 or similar.. just displays time and if you press something "5 restaurant unavailable"
I was able to change language by pressing and if I press and hold # I get some "menu" with digits 1 to 8 but nothing more... so it ses to be ok just locked or frozen.. How can I reset the pk5500 keypad to factory settings or did I just bought a defect keypad and nothing can be done?..

Thanks in advance for any tips! Google is fed up with me and doesn't give any new tips..

Sorry OP Ive never worked on a DSC system

However it sounds like it configured to only talk to its previous panel which is obviously unavailable. Id assume there is a reset procedure that may require the old keypad to program the 'new old' one in