This weekend my 2020 GMC Sierra starting blowing cold air on the drivers side floor vent while the passenger side was blowing hot air. Is there a procedure to reset the blend door?

AC or heat reset
Turn the system on full cold Max AC.
Radio OFF.
Turn ignition OFF.
Pull the HVAC (AC) fuse(*) from interior fuse box. Leave out for 1 minute and replace.
Turn key to run/on position....NOT start.
Do not touch any controls. You'll hear the doors (actuators) being opened and closed. The HVAC module is learning the full open and full close positions. Wait until the system is completely done with the learning process. Less than a minute.
Start and test the system.

There are 2 fuses for the HVAC. I tried pulling both at different times and at the specific time with no luck. I followed your instructions and it has not reset.

May need an actuator.