My old garmin 2 won't connect

There are several Garmin "2" devices. fenix 2 being the oldest. Which one?

fenix 2, vivofit 2, Swim 2, Venu 2, Instinct 2, Enduro 2, Edge Explore 2.

Thanks. I would follow the procedure in this video. Key points are to make sure your old phone is not still paired with the Swim 2 and you have the Swim 2 in Bluetooth pairing mode. 

If still issues, follow the advice in the more extensive Sync / Connection Troubleshooting Guide

After that, it's on to Garmin Customer Support