Sorry, I can't help you there. I'm better with wires than apps I'm afraid.
I have never installed one of these type of thermostats, I am aware of a few folks who have had difficulties of one sort or another with similar looking Chinese units they picked up from Amazon. I don't know if they managed to get them working in the end or not.
If the app won't accept the password, It would appear that either the app or the password is incorrect, so only the manufacturer would be able to help with that I would suspect.