I've never been able to do a toe-pushup. Until today....I did 2!
(And all I do for upper body strength is barre...lots of planks and pushups and such). I think one thing that has helped lately....stop modifying on my knees. Instead, I do just micro-bends (pushups from my toes, but just barely bending my elbow). Eventually I could bend a little more and more.
I still can't go all the way down, but enough to make me happy!