Does the machine have auto-dry cycles, or only timed? If both, does the problem of the timer not running happen on both, or only on auto-dry? No heat (or insufficient heat) could be related to the timer not advancing. On the auto-dry cycles, the timer does not advance until it heats to the target temperature. Flaky heating on a gas model often points to a bad gas valve/solenoid.

Thank you for the response..
The timer did advance during the timed cycles but the heat problem remained.
I removed the front cover and observed as I started the unit in both the timed and auto cycles..The igniter would get cherry red, and I would get flame but the flame seemed lazy and the system would shut down after about 5-10 seconds..I replaced the gas solenoids (2..one three pin and one two pin)..I had the exact same problem as prior to replacement..
I decided to pull the unit completely out from the wall to clean behind it and to clean the vent line...With the vent line removed, I tried again and the unit seems to be operating correctly...I did not find much lint in the vent at all as far as I can reach, however it is about a 12 ft run with about 6ft of that being verticle...I have a large shop and I am going to try to blow the vent line to see if I can clear any obstruction that may exist.
Please keep the suggestions coming..
Thank you so much for your time.
Steve