I have a 2016 Explorer Sport, and when I try to use the keyless entry I get a red dot at the top of the panel and nothing works. Any suggestions why this is happening? It worked before but now all of the sudden its no-op with that red light at top.

 

Is the red dot on all the time? Does said red dot respond to the buttons being touched?

 

No the red dot comes on when I try to use keyless pad and then there is no response from the keys

 

Ford just wants to replace the entire thing @ over $500

 

Ok so if the red dot comes on you've got power and ground. I would agree just replace the trim panel, every keyless entry pad fault I've seen has been the key pad itself.
The part ranges from $200-$300 usually and I believe labor time is around 1.5 hours so honestly the quote sounds right.
If you are willing to fight/cut your hand up a little with routing the wiring through the door for about an hour or two I can post instructions for how to replace it so you only have to pay for the part.