My iPhone 6 Plus upgrade

If it is showing that there is an update, then you need to go to settings>general>reset>and reset the network settings to see if that helps. Check Settings > Screen Time > Always Allowed > make sure there is nothing restricted. Check Settings > Screen Time > Content & Privacy Restrictions and make sure nothing is restricted.

I do not understand your question.

1. Are you talking about the latest iOS update.
2. Or are you talking about the upgrade program to get a new device?