Perhaps this:
My request for a Colorado ID on iPhone and Apple Watch needs additional verification – what does that mean?
Customers will see this notification when their request needs additional information, via a verification letter sent to their address on file with the DMV. Once they receive the letter in the mail, they will navigate to e-Services on the DMV website and enter the verification code provided in the letter, in addition to a few other data elements that are used to verify their identity. Alternatively, customers may need to meet with an agent in order to move forward with enrollment. For more information, call (303) 205-5600 for support.
If the first person you spoke to was unfamiliar with the process (not surprising as it's relatively new), you may have better luck calling back and asking to speak to a supervisor or by going into your local DMV. Ultimately, this is someting you're going to need to work out with the DMV, though.