Perhaps you have already tried to register a unit with a new IMEI in another account?
Could you send us more detailed information. Please indicate your login, where the old unit is registered, by which the data was received before. Also, please indicate the old IMEI of the tracker, also please attach the photo of the tracker on which this old IMEI is indicated, if it is possible, and also ask the tracker for the current parameters and attach a screenshot in which the response with the new IMEI is visible.
You can write to us about the problem at firstname.lastname@example.org.