HTC One User Manual page 19

If the PIN code doesn't appear, this may mean that your old phone
is unable to connect to your new phone. If this happens, tap
Unable to establish a connection on your new phone to use
Bluetooth for transferring contacts from your old phone.
6. On your old phone, tap Next, choose the types of content you want
to transfer, and then tap Start.
7. Wait for the transfer to finish.
8. Tap Done on both phones.
Setting up your phone 19