I found the customers dryer vent clogged on the outside of their house, which caused the thermal cut-off, which is located on the heating element housing, to go bad.

I cleaned their outside exhaust vent, and cleaned their entire vent hose exhaust in the back of the dryer of all lint.

I unplugged the dryer, then disassembled the dryer and removed the drum to get better access to it, then I ohm tested the thermal cut-off and I got no continuity on my multimeter. I also ohm tested the heating element and the high-limit thermostat and both ohm tested good.

I replaced the thermal cut-off, reassembled the dryer, plugged it in, and it started heating normally again.

Here’s the thermal cut-off(also called a thermal fuse) for this model:
DC96-00887C
DC96-00887C Thermal cut-off

Western Arizona Forecast:
Tonight
Mostly clear. Lows 58 to 68. Southwest wind 5 to 10 mph.
Tuesday
Partly sunny. Highs 93 to 98. South wind 5 to 10 mph.