Check coolant level.
Have dealer do a coolant system purge. Ask them to do it twice. This will get rid of any air trapped in system and if one of the coolant valve are not working it should show up while they are doing the procedure.
Try turning on Def. High. It is the red Def button above the on/off button on the hvac control panel.
Mine was not working and did this and have had heat on
Any setting ever since.
Worth a try and my save a trip back to Ford.