How do I resolve 'iPhone unavailable' issue on stored iPhone XR?

I own an iPhone XR 100% paid for! I got a new iPhone 13 and stored the iPhone XR in case I needed it at a later date for whatever reason. When my new iPhone messed up I got the XR out of the closet, plugged it up, charged it And when it charged up it immediately said iPhone unavailable! It didn’t give me an option to enter a passcode to erase it or nothing just said iPhone unavailable with the only option being emergency phone call. I don’t care about what was on the iPhone because I got everything I needed off of it before I even stored it. I just need the thing to work because I paid for it. I own it. Can anyone tell me what to do because I’m seriously on my last leg with Apple they have been nothing but a pain in my neck constantly.

[Re-Titled by Moderator]