Using Fairbuds with older bluetooth transmitter

I recently got myself some fairbuds which I’ve been using without any issue with my android phone, however I’ve been slowly moving back to using my iPod classic for a lot of my music listening. I got a cheapo adapter for using bluetooth with my ipod which worked fine with the fairbuds, but was pretty awful quality ways. I decided to get a nicer Kokkia bluetooth adapter to use, however I’ve found it impossible to connect the fairbuds to it. The adapter is switched on and pairing as soon as it’s connected, but putting the fairbuds into pairing there’s no connection made between them. I’m wondering if anyone else has had issues getting them to pair with cheaper bluetooth transmitters, as I’m a bit lost as to how it can connect to one and not the other, unless it’s a codec issue.
Any advice would be greatly appreciated!