A/C doesn't work after long drive

2001 cobra convertible -- drove it 4.5 hrs yesterday morning getting home after fathers day -- preformed great, top down all the way -- everything nominal -- ran into an isolated shower at home and after i got the top up -- turned on the a/c -- just got hot air -- i had used the a/c a couple of weeks ago and it worked fine so i was surprised -- started it up this morning -- a/c works fine --

so the failure seems to be related to the long drive -- appreciate your thoughts on what is going on --

larry