Hi Bob,
If the furnace blower is working but no heat, here are the most common reasons the furnace burner did not come on. 1- the propane detector got turned off or you are out of propane, 2- the furnace limit switch has failed and will not allow the ignition circuit to activate, 3- mud daubbers wasps have built a nest in your furnace combustion chamber, they are attracted to the ethelmercaptain chemical they put in the propane to alert you of a leak. By the way, Texas is full of mud daubbers, 4- the ignition circuit on the PC board has failed because the furnace is 22 years old.
Hope this helps, Fred Brooks