Check of knob indicated several areas where the plastic had dried and cracked, becoming too loose to allow the knob to turn the timer.
Purchased a new knob from AppliancePartsPros.com and received the new knob within several days. I was pleasantly surprised to find the new one to be the exact copy of the old (without the cracks of course), Within minutes, I had removed the old knob and replaced it with the new one and had the dryer working at full capacity again.