Is it a Leaf back (from the original Leaf company), or have you sent it in to have it checked and modified by Phase/Leaf? Only Phase/Leaf backs that they've either sold since Leaf was bought, or have been sent in and paid to have them upgraded. Otherwise.. no tether (although you can still tether with Leaf Capture)
(still, in my mind, this isn't quite right.. I know Phase says they can't be responsible for Leaf products bought before Leaf was acquired).. but i don't think they require people to send in their Canon or Nikon cameras for a paid upgrade before they can be tethered to Capture One) I *love* my 75S.. and would never trade it in for anything other than another Leaf back. One of these days, i'll end up with an upgrae to a Aptus 10 or something.. and that problem will be solved.. but as a Leaf customer.. i've always felt that rather then happily helping me as a customer.. it was always a begrudging task on the Company's part. In contrast, I've owned a Betterlight scan back since 2001, and I'd recommend their support over any other companies (of any product)