This is a tough one. The only other thing I could think of, was to get its ecu reset. Maybe it’s in a protective/diagnostic mode which is preventing it to go into EV. When you driving, I know you don’t see the EV sign light up, but do you see average improving in the “live” average meter?
There is one other thing that keeps the EV mode away, maybe there is a link. When the Driver’s door is open, my car doesn’t cut the engine. So I’m thinking, maybe a faulty sensor? Besides these, I’ve run out of guesses.