2017 no heat on drivers side

Had my coolant changed at 100k. Heat worked before that. Now I only get heat from passenger side. But I do hear a loud whirring sound from the top left of the dash when messing with the hvac controls. Any advice on what I could check at home would be welcome. I also purchased a 4 year, 48k comprehensive warranty when i bought the truck with 99k miles, do you think this would be covered? I had the coolant changed at the dealer, it was bright pink at first and now its back to the same mix of dark pink, is that normal for a coolant flush from the dealer?