Checking in for codeshare flight: valid ticket coupon not found
I am trying to check in for a flight that was sold by US Airways but operated by United. When I go to the US Airways website, I get an error that says to go to the operating airline (United) to check in. When I try to check-in on United, I get the error: "We are unable to complete the check-in process as a valid ticket coupon cannot be found. "
Is this normal for codeshares? Or some glitch related to the system transition last weekend?