Make sure that your iPhone, iPad, or PC has a strong internet connection and that you've turned on cellular data on your iPhone or iPad by going to Settings> Cellular or Cellular Data. With this setting turned off, you may not be able to access your Apple ID and iCloud if you are not connected to a Wi-Fi network.
Why Apple Password Not Working
A lot of people have encountered the following issues:
Apple password not working
My iCloud password is not working
My iTunes password is not working
Well, there are several reasons for this. It's usually due to the Apple server issue, or someone else has changed your Apple ID password. Numerous methods can assist you to sort out the puzzle. Let's discuss them in detail. https://www.wikicue.com/apple-id-not-working-on-iphone/