After checking the manual, it showed that there were two possible reasons. I further diagnosed by going online and finding out that most of the time it was a relay that was stuck that caused this issue. On this model of Samsung dryer, the control board had to be replaced. Once I received part, checked to ensure it was the right one backed on Samsung's website photos. The replacement was simple. Unplugged dryer first. Two screws on back of dryer to remove top. The board inside a metal housing that has 3 screws attaching it to the top left side. Remove them and slide forward to remove. Flip it on its side exposes the control board. There are several connectors that had to be removed. Squeezing the top released the tabs and you pull. They are color coded and different sized making it impossible to reconnect wrong. Took a picture before I removed. The board must be somewhat universal as there were a couple extra connectors that weren't used. Once plugged in reattach board with one screw to metal housing and attach back to side. Then before replacing top, I plugged in dryer and tested. It ran only when door was closed. Replaced top and slid dryer back in place. The time to replace the part, was about 25-30 minutes from the time I walked into utility room to having it put back together and back in place. Knowing what tools you need, where the part is located made it easier. Most likely the easiest part to replace on the dryer.