If your Haier microwave runs but is not heating, check that the door is closing properly. Open and close the door firmly, but do not slam. This confirms the engagement of the door's safety mechanisms.
Try unplugging the microwave for 30 seconds to reset it. If you continue to have problems, please contact Haier Appliances at 1-877-337-3639 or visit https://www.haierappliances.com/support/schedule-service to arrange service.