I  would suggest putting new batteries in the remotes, and also (this
applied to all of the GM vehicles I have owned) try closing all doors, car
off, and press and hold both "Unlock" and "Lock" buttons at the same time.
After a minute of so, the van should honk it's horn, flash its lights, or
something.  It usually worked on my cars, and is even in my driver's manual.

I was wondering if anyone has had a similar problem to ours.  We seem to be
having problems with our remote locks.  On my keyfob the door lock and the
panic alarm buttons work fine, but the button to unlock the doors does not
work.  On my wife's keyfob she can open the doors "sometimes" , but  more
often than not it will not open.  She has better luck with locking the
doors, but sometimes it just won't work.

Any ideas on the cause and the fix?