Hi mweaverpdx,
You certainly have run the gamut here on possible solutions. Curious to know if the previously connected AirTag still shows under your Apple ID.
It may be worth checking and trying to remove your AirTag from your Apple ID on your iPhone to get your AirTag connected again:
1. Open the Find My app, then tap the Items tab or Devices tab
2. Tap the item or device you want to remove, then swipe up on the handle

3. Tap Remove Item or Remove This Device, then tap Remove to confirm

Did the person you mentioned working with provide you with their contact details? You could always give them a ring or reach back out through Apple's Get Support site.
All the best, my friend.