Hello NJAnalyst,
Thanks for posting in the Apple Support Communities.
It sounds like you've replaced the battery of your AirTag with a Duracell CR2032 battery, but still can't get it to appear on your iPhone, correct?
If we understood you correctly, let's see if a reset of your AirTag will clear this up. Check out the steps below for assistance with this, and you can also check out these steps here: How to reset your AirTag - Apple Support
Here's how to reset your AirTag:
1. Press down on the polished stainless steel battery cover of your AirTag and rotate counterclockwise until the cover stops rotating.
2. Remove the cover and the battery.
3. Replace the battery.
4. Press down on the battery until you hear a sound. This sound means that the battery is connected.
5. When the sound finishes, repeat the process four more times, removing and replacing the battery, then pressing down on the battery until you hear a sound. You should hear a sound each time you press on the battery, for a total of five sounds. The fifth sound is different from the previous four. This indicates that the AirTag is now ready to pair.
6. Replace the cover by aligning the three tabs on the cover with the three slots on your AirTag.
7. Press down on the cover.
8. Rotate the cover clockwise until it stops rotating.
Let us know if this continues after those steps, and confirm which sounds you hear after following those steps.
Have a great day!