I’m not sure why but the description of burn drive says if 4+ units (one has to be ally) are burned it would work. As far as i can see there are 4 burned enemies, 3 burned allies and i have easily enough spirit to activate the move, but it says I don’t meet the conditions?
You need to have a second fire ally on the field in order for it to work. If you read the description it’s actually in there, albeit hard to see.
If it makes you feel better i’ve made the exact same mistake myself as well.