Hi! I just wanted to share my experience to (hopefully) save another person's headache!
First off - I'm using .dai and Frosty mods. Second - my mod folders are located on my C drive, and my game is on my D drive. I don't know if those two things have anything to do with what my problem was but I just wanted to throw that out there
The only thing that worked for me was to follow the instructions in Food Then Games' channel, here; specifically her changes to the patch folder in your Dragon Age Inquisition game folder. I had a folder inside the Update folder called "Merged". I removed that, and Frosty started for me.