Why is my password not working on my new iphone?

I changed my password I can sign in on my computer but not my iphone

I'm not sure but if you have not got anything on it like apps or pictures that you don't want to lose on it then just plug your phone into the computer you set it up with, go on iTunes click under devices an press restore, it will then be like a completely new iPhone and won't even have a password on it then you just set a new password.