the glove box won't open

Sounds like the latch is stuck, or perhaps the prev. owner had the keys changed for the door locks or ignition but does not have them keyed to to the glove box.  Suggest having a dealership cut a key by your VIN number and see if that opens the glove box.  There isn't any other button for it.

try this.... only if you want to buy a new glove box door.

http://www.matthewsvolvosite.com/glovebox_fix_850.php