I've just recently purchased a Gear Sport and having the same problem. I did some research and found out the Samsung Pay doesn't support Gear Sport which is ridiculous since their ads and product info said it's compatible.
The Gear Sport model code is SM-R600 (printed on the box) and here is the list of device Samsung Pay support
It supports Samsung Pay over NFC (Gear S3 and Samsung Phones work on MST technology). NFC terminals are hard to find in India. But Samsung Pay for wearables in India has not been launched yet so it doesn't make much of a difference.
Thank you for reaching out to the Samsung community! Kindly follow the link below, it has all the specs supported for gear sport in India and it's no where mentioned that s pay is supported. http://www.samsung.com/in/wearables/gear-sport-r600/SM-R600NZBAINU/
Be sure to hit ♡ when you find an answer that works for you. For Further assistance, you can get in touch with us via Live Chat option by following- http://livechat.support.samsung.com/Customer_new/IN. You can also connect us via Samsung Members web community by following mentioned url-https://community.samsungmembers.com/en_IN#/
