I just flew that same exact city pair yesterday. I wonder what happened to your flight.
We had the same thing happen to us. Bought airfare for spring break. Last flight out of SLC that could get us to Cancun that same day. One stop through Houston.
They canceled the SLC-HOU flight already. Earlier flights that morning are already full. Our option is to either go a day earlier or a day later.
It’s a big inconvenience. I wasn’t happy.