In very simple terms, (1) many broadcasters Apps won’t allow you to play back downloaded high-definition (HD) content on an external display - but will allow you to stream a lower-definition version of the same content to the very same external display.
Some broadcast content is protected by copyright (2). There are technical measures that ensure that this content can only be played back if every component in the chain of hardware supports HDCP. If any component in the connection chain doesn’t support HDCP, the video portion of the broadcast will not display.
Not all monitors/TVs incorporate the special HDCP hardware - and for those don’t support HDCP, any copyright protected HD content cannot be played back.
In summary, you are very unlikely to have a technical fault - but are more likely to have encountered either an intended restriction to playback by the Broadcaster/App Developer (#1 above), or copyright protection enforced by hardware (#2 above), or a combination of both.