If it is saying password or email wrong, and you are sure that the password is right, it must be the email address.
You may be typing this correctly now, but perhaps you gave it wrongly initially, or used a different email address then?
A good way to check the situation is to take the Forgot Password? link, and give the email address there. If it can’t find you under that email address, then you will know you have it wrong. And if you think you might have given another email address, you can try that.
But if the email address is accepted, carry on, and give what you think is your password again. If it wasn’t that, it should accept it, and then it will be your password going forward.
But if it was that, it may refuse it, and you can set a new one, double-checking that you got it right.
And then go back to the itv hub to see if it now works with the refreshed details.
I know this might sound like a silly question on my part, where i am assuming you are not using your nowtv account details whilst attempting to either setup or sign into the ITV Hub App on your box ?
Where you need to sign up via this link below on the ITV Hub website to use the ITV Hub App on the nowtv box or stick and haven't been resetting your nowtv password by mistake by going to your nowtv website login.
Obviously ignore my post if you are using your ITV Hub account and not your NowTV account details.
Until the ITV Hub version 2 app started to appear recently, the app only ever required you to input a postcode to use it.
The V2 app now requires you to create a ITV account, which may be a ITV Hub account rather than a ITV account?