To unbind a device whose SN is already registered, you can try the following steps:

1. Log in to your IAMMETER account at iammeter.com and go to the device list.
2. Find the device you want to unbind and click the settings icon.
3. Look for an "Unbind" or "Remove" option in the device settings.
4. If the device was previously bound to another account, you may need to perform a factory reset on the meter itself (hold the reset button for 10 seconds).

If the SN is stuck in "already in use" and you cannot unbind it yourself, please contact IAMMETER support at [email protected] with your device SN, and they will manually unbind it for you.

Tip: If you just received a second-hand device, ask the previous owner to unbind it from their account first, or provide proof of purchase when contacting support.