Southwest Routing Question

This is a very stupid question from a newbie, so forgive me.

My closest Southwest Airlines airports would be either Pensacola (PNS) or Panama City Beach (ECP). I'm looking at a trip to Montego Bay, Jamaica. But when I search from those locales, I get errors saying no options available. Which seems odd since I could certainly fly to Houston, then Houston to MBJ. One stop.

Any help is appreciated as to why I'm not seeing availability at all.