I have replaced the heating element and the two thermostats. It still is not heating.

Thank you
Jerry

Here is your parts breakdown
Model LET8858DQ1

Here is the wiring diagram
https://www.servicematters.com/d...0Sheet%20-%203401725.pdf

Have you checked that you have 240 volts at the receptacle.
Sometimes you can loose half the line without actually tripping the breaker.
Try turning the breaker off/on a couple times slowly.
Depending 3hich side drops out the motor will run but you will have no heat.

Have you checked the Thermal Cutout (see the wiring diagram).
Item 9 in "SECTION 3".
To check you could short the wires together and tape them up so they cannot short to anything. Then give the unit a try.
Do not leave the unit like this as it is a safety device.
If required replace it ASAP.

If it is the Thermal Cutout give the interior a good cleaning including the blower wheel.
Also clean and check your vent system