@board4mic May I ask have you tried on any dimmable smart switch to realize a 4-way switch? 

  @xRkYqUz Have you got answer of your previous question? 

  @RichG5 Is it dimmable smart switch, the one you replaced? 

  @septer012  Does the 4 way switch need to stay untouched?  I'm having trouble once I move the 4 way switch to on/off

  @rv75 4-Way switches don't have an on or off. They have a "this" or "that." They also have a long break-to-make time that can kill power to any Kasa downstream. Check out my video. The animation at the start may be of help. https://youtu.be/kMT7KUVTELo

  @rv75 Yes, it almost certainly sounds like something is wired wrong. If I had to guess, I'd say that one of the travelers has been swapped with the load wire in the load-side box. (You'd have to beep it out with a multimeter to be completely sure.) This assumes all was working before the HS-210s were installed.

Despite what people say, 2 HS-210s are never "required" -- in fact, the 2nd one doesn't really add much to the system beyond an aesthetic similarity.

  @PatchyFog 

thanks again!  I might've screwed the wiring up because the first time I connect the HS210 nothing was working. 
Am I supposed to have only one hot wire on common and the other 2 on travel? Besides the obvious neutral and ground?

  @PatchyFog Sorry to bug you again... I rewired my initial HS210 (hot black wire on common and red/black wires on traveller.)  I'm still having an issue.  Could the switch be defective?  When I use my second HS210 and the 4 way switch, everything works perfectly.  The minute I try to use the first HS210 to shut off/on the light after using any of the other switches, the lights go off and don't come back unless I start playing around with the other 2 switches and the app.  Something is not working right and I can't figure it out.

Just thought of something.. The only difference with the first HS210 I installed is that the "dumb" switch was not using the white neutral wires.  The HS210 needed them so I am using neutral now on that location.  Nothing else is different.

  @rv75  Finally figured out my wiring issue.  I had correctly labeled the common wire but the HS210 initially didn't work well.  I guess it was because of the fact that I needed 2.  I swtich the wiring around and it made it partially work.  Dissecting the diagram is what really helped me.  The 2 wire cable was the common and I had moved it.  Now I have the travellers coming from the 3 wire cable and all seems to be good