I purchased an H fare for KA192 (HKG>DAC) from the CX website. Ticket was sold as CX6192. After checking in at the AE station in the morning I decided I wanted to upgrade using AM. J was wide open so I didn't expect any issues. I was first denied at the KA check-in counter at HKG. They said this could not be done as the ticket was purchased from CX.

I checked again at The Wing F lounge and was initially told it does not matter where the ticket was purchased but only the fare class. As I was on an H fare I figured great.

Later the lounge person came back and told me the same thing as the check-in agent.

Is this normal? I didn't see this requirement anywhere in the T&C on the AM site.