subscription-manager: Why am I unable to download some content (like FasTrack) or getting 'too many content sets for certificate' error?

Issue

• Unable to download certain packages (like FasTrack) when using subscription manager
• Problem registering or subscribing due to cert error: 'Too many content sets for certificate. A newer client may be available to address this problem.'
• Not able to attach some subscriptions (such as Red Hat Enterprise Linux Academic Site Subscription (Server, Desktop, Workstation, POWER)), or above a number of subscriptions, to Subscription Asset Management Organization