I got a Garmin Montana 700i that I bought used. I am trying to set up the InReach messaging set up but I consistently get an error message "Invalid Unit Number". The person I bought it from bought it new in 2022 and used it twice (it looks brand new). He never set up InReach previously. I headed on a trip in 2 days so I really need help fixing this, but I can't find a support email or chat. It was factory reset and the software has been updated (version 20.30 (dad15fb) and the maps have also been updated. I've tried activating on the paired Messenger app on my phone as well as on the device itself. Also tried connected via cable and outside in an unobstructed area. Can anyone help?