Here's one possibility. I've noticed the NH website is very picky about how you enter your name to search for the reservation. If you have your middle name or middle initial on the ticket, then you need to include that in order to pull it up. It's not very obvious since it only asks for your first name.

For example, if your name is John Gregory Doe, you'll either put in "JohnG" or "JohnGregory" for the first name. The system typically will not find it if you just put in "John".

I've had success using both the NH PNR and eticket number I received from CO on an award ticket, but since my CO account has a middle initial I had to include that to see the reservation. Took a little while to figure that out.

Hopefully that's helpful.