why won't the doors unlock when i approach the vehicle with my key fob ?

Does everything else work with the fob? Perhaps it needs to be reprogramed if all other functions are working. I've seen people place their car keys on the magnetic pads at checkout counters that are used to cancel the security chips in products. That will scramble your fob if it is done. Sometimes other cars or electronic items will interfere and mess with the fob signals. You have two fobs correct? Does the other one also act the same? Perhaps reprograming the computer will fix it, or the computer is causing the issue. Test the battery first, then try the reprograming. Then have the computer checked. New fobs are expensive.

How to reprogram the fob?