Why is my I phone XR saying it is unable to read battery optimazion

Did you replace the battery recently? If you did, it appears that non-genuine Apple battery was installed. Maximum Capacity will likely be no longer displayed correctly, if it is displayed at all.

If you did not replace the battery, check Battery Health / Maximum Capacity. 80% or less, you need a new battery.

It can also mean that you have a genuine battery that is no longer working correctly. If you've never had the battery replaced and you're suddenly seeing this message, make arrangments to have the phone evaluated:

Genius Bar Reservation and Apple Support Options - Apple

Did you recently get the Battery replaced? Your iPhone cannot determine whether the battery is a genuine Apple Battery or not.

Axel F.

Can you post the exact error message that you are seeing? Is this related to Battery Health Percentage or Battery Optimization?

Axel F.