Why does it seem like there's no HDMI output from my Galaxy Tab 4?

[AC Question]

I have both (a) the micros USB -> HDMI adapter and (b) HDMI -> HDMI cable. But when I hook it all up to connect my Tab 4 to my flat-screen TV (with the TV on HDMI input), the TV says "no signal".

I have even tried using the HDMI -> HDMI cable that works when connected from the cable box to the TV, so I know the problem is not with the HDMI -> HDMI cable.

It appears that there's no HDMI signal coming from the Galaxy Tab 4, even with the adapter.