Coinbase is unable to verify me. What should I do?
We know it for a fact that in rare instances Coinbase may be unable to verify your identity or even the phone number you used at registration. Unfortunately, that's one of the downsides of quick growth as they grew almost ten-fold in 2017 alone.
If you got stuck at phone confirmation stage, try using a different phone number, if possible.
In any case, please reach out to their customer support and wait for further instructions.