Okay, now I'm really regretting buying this camera KC120.

Bought this camera to monitor my maid's activity, and installed initially in the baby's room.

When I'm at home, the live view is not bad. Both view and sounds works.

When I'm outside of home, all the problems come out.

1) When trying to view the live view, nothing comes out. Only the stupid circle thing keep rotating. So no live view outside of home.

2) When trying to view the video taken in the activity tab, 95% of the video cannot be viewed.  There's a cross on it, and it says "Clip Unavailable, the clip can't be played because something went wrong while uploading from your Kasa Cam."  The other 5% only has 1 second of the video.

Then I'm trying to search around for the solution. Apparently there's a lot of people having the same problem.
I thought there might be a problem with the wifi signal.

It's NOT.

I put the camera right in the living room just besides my ASUS router within half a meter distance with no obstruction, and my wifi in the living room is fast enough to have low latency for all kinds of online gaming.

The problem stays the same.

The signal light on the camera is a steady green, which means it's successfully connect to both wifi and cloud.
However, clip recorded in the living room still cannot be played.

So the camera only have a live view function when I'm at home, which completely defeats the purpose of getting a camera.

It looks like an immature product to me. 

Lesson learnt, have no faith in TP-link products any more and will avoid its products from now on.