XC90 clicks but wont start
 

Hi everyone. My wife's '10 XC90 3.2 has a serious starting problem and I am at my wit's end. Any help will be greatly appreciated before she and my kids trash my super rare Jaguar Super V8 they are using in the meantime! :(
Last year her XC90 would click once then wouldn't start and our mechanic changed the starter. It still wouldn't start until we tried her extra valet key (small but I guess has a chip in it) and it worked!! The big key with the remote controls would work very rarely so she just kept using the valet key. Fast forward a year to last month and occasionally she would get the clicking but no start using the valet key. It kept not starting more and more often until it wouldn't start at all. It is now at the shop and we've replaced the starter ( was still under warranty) and put a brand new battery and still no start. The mechanic says the computer is getting the signal to start and he has checked the starter solenoid wire, replaced the antenna ring around the ignition and still no start. I called Volvo and they are telling me depending on what's wrong it, it could run from $500-1500 or more!. Please help! I am suspecting that both keys are defective. Thanks for any help.