A lot of this going around
Having the same problem. Tried on a PC running Windows 10 and two Macs running 10.6, 10.10 and 10.11 with different cables. The v650 charges but isn't recognized by Polar FlowSync.
When I contacted Polar support I received the following message.
"Thank you for your email to Polar USA Customer Support!
*
Your e-mail message has been received. *We are currently experiencing a high volume. We will do our best to respond to your inquiry as soon as possible.
Thank you for your patience and we apologize for any inconvenience caused."
Will return it if I can't find a solution soon.