Have a look at this pdf, especially on Pg42 (by document viewer page #) which shows the immobiliser circuit.
http://www.myvolvolibrary.info/Tech_..._98_Wiring.pdf
I might be wrong on this but it looks to me as if there is a combined alarm/immobiliser operated by a fob, rather than having the RFID chip. If so, do you have the alarm fob for the car? Again that should be with the key or perhaps, integral with the key.
See how you get on with the landlord getting the key (and hopfeully the alarm fob if it's separate) back and hopefully you'll be able to start it.