How do I remove a message about my battery not being a genuine Apple battery?

Two possibilities:

1) The battery was replaced with the wrong part. Now Battery Health and other important info will likely not work correctly

2) The battery is failing and it will need to be replaced at an Apple Store or authorized Apple Service shop

The message that you see will continue to be displayed until things are fixed

Find Locations

Click on the link for an explanation of that message in the article 'About genuine iPhone batteries' --> About genuine iPhone batteries - Apple Support

"An Unknown Part  message will appear if the battery installation is incomplete or if the battery:

• Was replaced with a nongenuine battery

• Was already used or installed in another iPhone

• Isn't functioning as expected"

I guess the remedy is to make sure none of the above apply.