version 10.7.2 for Mac broke the ability to connect to an RD Gateway. Rolling back to previous versions restores this ability.
Sorry that the new update hasn't resolved your issue, based off the comment "No, I received the same error message as when I used the most current version 10.7.2 and 10.7.3." then your issue does appear to unrelated to the load balancer changes in 10.7.2/3 and therefore the resulting patch in 10.7 and unrelated to this current thread.
That said, if we cannot use a test account a repro your issue, a good place to start will be eliminating the possibility the issue is unrelated to macOS, can you please try connecting to your remote resources with the Windows Remote Desktop client and if the behavior is only reproducible on macOS create a new thread. Thanks!