Unable to send run from Ipod Nano to Nike+

I have recently been encountering an "iTunes could not connect to NIke+. An unknown error occurred (400)." message when attempting to sync.

I have synced my iPod many times before, as I have tried on the latest version of iTunes (12.2.2.5) on Win 10, and a much old version (11.2.2.3) on Win7. Receiving the same error on both machines.

My network connection is active and working, as I can connect to the iTunes store and use my web browser.

Any ideas on what could be wrong?