Check behind the dryer and listen if you can hear the drive motor coming on. There possibilities are that either your belt is off, that your drive motor is not working or that your belt switch is not working. you can get the service manual from here and page 4.7 will help you to figure it out. Of course, your fancy dryer also has a diagnostics mode that might help you with your repair as well. Hope this helps, good luck.

The HE3 dryer appears to be same as/similar to the Whirlpool Duet Dryer

Are there any fault codes displayed?

Have look at the SERVICE MANUAL (click on Duetdry.pdf) - Section 4-11 details the drum, roller, belt and section 6-1 for error codes and diagnostics

HIH