Hi there, @GarethV. Firstly, I'd recommend consulting the guide below (from our colleagues at Samsung Singapore):
Some of the information towards the end of the aforementioned guide will only be relevant to that region, but I'm sure you'll see that.
I'm not sure where you purchased the replacement Bud. However, if the guide does not facilitate you in getting your Buds Live synced, then our In-store engineers will be ideally placed to ensure that you get these synced again:
Please let us know how you get on.