How to avoid gas freezing
It's not, exactly, frozen. Liquified Propane Gas maintains a pressure in the tank proportional to the temperature of the tank/gas. You might have noticed that the tank was quite cold - as you use gas, the liquid in the tank boils to replace it, and the boiling of the liquid takes heat (latent heat of vaporization) so the liquid and the tank cool as gas is used. If they cool too much, the pressure in the tank drops below the pressure you are using form the tank.

If you are managing to cool the tank to the point that (useful) gas pressure is lost while the air temperature is 80°F, you need a larger tank to supply whatever (presumably fairly high-output) burner you are feeding. Or you need to check for what could be a fairly major leak, if this same setup used to work, and suddenly stopped working without you doing something like adding a larger stove or turning on all the burners at once, if you don't normally do that.