Won't stay running

I have a Frigidaire Affinity dryer that won’t stay running.
It turns on and it heats up but only on Timed dry. I can change all the settings but it will not run longer that 20 turns on any cycle but timed dry. The longest it will run is 20 mins on timed dry. It beeps the control panel lights up and blinks on and off above start/Pause. When I hit cancel it turns off but it will automatically turn the control panel only back on. I have received no error message ever. I have tried the factor reset and it does nothing. I did not receive a error message when doing this. I have unplugged and replugged that does nothing. I do not want to change the control panel board if that is not the problem. Thanks for all help.