inability to pair

After using my Apple Watch for about 1 month it was unable to sync with my iphone 6. I therefore un-paired it and am now trying to pait it again. The pairing process starts as usual, the pairing animation works to identify the watch, but then the process get's stuck after selecting to pair based on last backup (same result if I check to restart without using backup - the process stops when selecting left or right wrist).

Iphone is on iOS 8.4. Tried restarting both decives, but no result.

Unsure if this is because of faulty iphone or Apple Watch. Any suggestions how to proceed?

Thanks, Pat