you have three thermostat which one did you replace ?
One on blower housing ,one on top of heating element housing ,one on bottom of heating housing.
ok unplug the unit from the wall and on the blower housing you have the operating thermostat two red wires and two purple wires,
pull the two reds off the thermostat ,and put them together ,plug the unit back in set timer to a timed dry cycle ,and start the dryer and look to see if it is heating ,from the back you can see the GLOW of the element if it does heat .takes about 30 sec.or so .
Try this and I will hold on
ok so both ,the one on the blower housing ,and the one on the side of the element housing (Bypassing them did not make it heat)
And you have replaced the thermostat on the bottom of the housing and the heating element is that correct?
Sounds as if you have a stuck float switch or bad switch .
And you replaced the thermostat on the bottom of the element, and we /you Bypassed the other thermostats ,and still no heat .
And if it was the thermal fuse on the blower housing the motor would not run .
So you have to have a bad timer .
here is a link to the part .
the power comes from the timer to the one on the blower housing to the one on the top left side of element then to the bottom on then into the element.