I know it sounds silly but what you really do ? Cause for me personally when i turn on defog itself as usual the car basically blow cold ac air on windows and most of the times it just doesnt work that good. And i tested it on multiple cars. I tried just setting the car the blow outside air with no ac and that kinda works better. And recently i actually turned on heater to blow on windows and specially with ac on at the same time with heater and it works much better
Defroster, heat and A/C on. Try and keep your mats clear of ice and snow to keep it from repeating. RainX makes an anti fog spray for the inside windows, it’s pretty inexpensive and will help.