Here is my suggestion ... I'd like to see the vcloud-container-debug.log file that shows your error state.
Without a debug log containing the error state I/we cannot tell you why the login failed. the message is generic and can mean about 10 different situations. e.g. too early, too late, doesn't contain certain data, authentication failed, authorization failed ...
If the log provides too much information for a public forum, then you'll need to file a support request and provide it there. e.g the debug log contains some user information, IP & hostname of the cell it came from, and some other data.