Roper household dryer not heating (by 2 users)

Wife noticed the utility room was warmer than normal while checking on status of laundry this morning. No odors, just warm. She checked again later to find clothes not dry. I disconnected unit, pulled off back cover, cleaned and inspected. I found no visible problems. I did not know if this unit (Electric) has a thermal fuse to replace or reset type to get it going. If not, please help me determine if it is the thermal cut-off or the Hi limit thermostat or the heating element itself that needs replacing. The unit says to see if the heater box thermal unit is open.I was unable to figure out how to check that.
Thanks for any help you can give.
Kevin
dryer runs, but no heat. cleared exhaust obstructions, how to reset?