Could not Sign in iTunes & App Store from iPhone 6 Plus for "Your apple ID or password is incorrect".

Hello RomanpaxZhang,

Thanks for contacting the Apple Support Communities. If you are able to sign into the iTunes Store on your iMac and your iPad 2, but not on your iPhone 6 Plus, try the following:

1. On your computer, sign into your account at appleid.apple.com.

2. While signed into your account, check your billing information in the Payment & Shipping section. You may need to re-enter your credit card expiration date and security code. Make sure the billing address matches the address that the bank uses. Click Save on the right side of the window to save your changes.

3. Sign out of your account on your Mac.

4. On your iPhone, close any iTunes Store, App Store and Music apps that you may have open on your iPhone.

5. Restart your iPhone.

6. Tap Settings > iTunes & App Store

7. If you see an Apple ID, sign out and then sign back in with the Apple ID and password you just updated on your Mac.

8. Press the Home button on your iPhone.

9. Tap the iTunes Store. Are you able to access it now?

RomanpaxZhang, I'll include some resources below with more information regarding the steps I've listed above.

If your issue still persists, please reply back and we'll investigate further.

Managing your Apple ID

Force an app to close on your iPhone, iPad, or iPod touch

Restart your iPhone, iPad, or iPod touch

Sign in to the iTunes Store on your iPhone, iPad, iPod touch, Mac, PC, or Apple TV

Have a great day!

I Could not resolve that problem through your help. Please re asap... thank you...