FYI - I have flown a 140+K this year, and got this same message on my last 3 check-in's. I tried scanning my passport again, and that did not solve the problem. I found out that CO has updated/changed their software, and if your full name on your passport is not exactly the same as the name on your ticket, you cannot check in online (ie. if you use your First Name and middle initial on your ticket, and your passport has your middle name spelled out, the system kicks you out and will not check you in).