I think this is the same problem as Status code: 403 for Error: Failed to download metadata for repo after upgrade to 3.11, which was discussed quite extensively there.
tl:dr: There is a problem with candlepin 4.4.10 (I guess that is the version you are running?). That issue should be fixed with an update to candlepin 4.4.12/4.4.13, but those versions currently struggle with other problems that are also described in that thread and for which currently only workarounds exist.
