@Ferinthul 

Ferinthul ... could it be that I mixed up my line and load?? The line is coming from the non-3 way wire (I believe from the breaker) and the load coming from the light.

 

I also wired the bottom switch the same and couldnt get anything as well... How do i ensure the 3-way switches received are functional?

In a three-way wiring config, you have 5 relevant wires total in the box (not including duplicates for neutral and ground) 

In the box with the Line Supply from breaker 

One - Line from Breaker Box (this will also have a Neutral and Ground in the incoming Romex) 

Two & Three - the Travelers which go to the other switch (again will have Neutral and Ground which makes a 3 conductor plus ground cable) 

Then the Neutral (Four) and Ground (Five) which will be paired together from each Romex cable and also connected to the switch. 

It's essentially the same at the 'Load' end switch, except the 2-conductor (plus Ground) Romex goes to the Load (the light) 

So in the incoming Line Box, there is no 'load' per se, there are a pair of output travelers which run to the 'other' (load end) switch. 

When you operate that std dumb switch, it transfers power to one traveler terminal in one position, and to the other traveler terminal in the other. 

So when you say you have a Line Wire and a Load Wire in that first box that is not going to be the case - there is no actual load wire (from the light) that will be in that box. 

Now - some older homes have no neutral in the box - in which case they often use a white wire as one of the travelers. So it's possible you may be mistaking a white wire for Neutral, when it's really a Traveler. 

That would mean you could not use the HS210 as it MUST have a Neutral wire connection to function. 

There is a really simple way to tell if your white wire is indeed a 'real' Neutral, or if has been used as a Traveler - was it originally connected to the original dumb switch? If it WAS it is NOT a Neutral. (Neutral wires are NEVER connected to Dumb Switches) 

However if it is just tied to the outgoing Traveler Romex Neutral inside the box with a wire nut, then yes, that WOULD be a Neutral. 

But if latter is the case you should have three more wires (not incl ground) that would be the Line plus Two Traveler wires (you only mentioned line and load, which sounds like two) 

It would be helpful if you can show an image of your box with the switch not screwed in place so we can clearly see what you have. 

Also, not sure if too late, but always good idea to take an image of what you started with regarding connections on the original dumb switch, so you have that as a reference 

(or at least you sketched a drawing showing how it was)  

@Ferinthul OK, that is helpful - you definitely have a Neutral System incorporated so that is a positive. 

The Romex that contains the Black/Red/White/Ground - is the Traveler Romex - as an idividual entity it goes from one box to the other, nowhere else as far as line or load is concered 

So then you have a Black/White/Romex in each box - in one of these boxes, it is the Cable from the Breaker Box (the Line wire); in the other box, it is the Load Wire (to the light fixture) 

The important factor is to find out WHICH box is which - location at top or bottom is not necessarily an idicator or which. 

Do you have a Voltage Tester? (whether a meter or a non-contact type) 

If you don't, look up non contact voltage tester at HD or Lowes or Amazon - goot tool to have! 

What you need to do is turn breaker off and disconnect the black wire from the black/white romex) from both devices. 

Then isolate any exposed wires with wire nuts (the non-contact feature of the tester will allow testing even through the wire insulation) 

And then turn on the breaker and determine which box has the 'live' line wire

Once you establish that, this box is the ONE where you need to install the HS210 (the load one only needs the original 'dumb' switch - a second HS210 is NOT necessary)

It does not matter which traveler wire (black or red) goes to which travleler terminal - the line wire goes to the common and the neutral and ground accordingly. 

At the dumb switch end (load end) the incoming red & black traveler wires go to the two brass terminals and the load black wire goes to the black screw. 

You can tell when you have the HS210 installed on correct 'line' box in that you should be able to establish the WiFi connection regardless of the HS210 switch position. 

Hope that helps! 

p.s. One non-measurement clue which may help idenitfy which box is which:

In the two gang box - does the black wire in the 2-wire romex (the black/white/ground) also supply the other switch in the box? If it does, then that would definitely be your Line wire 

Also in your images - a little hard to make out, but looks like the black wire that you have tagged line/load appears to be coming from the taveler romex (the same one as the red wire)? If so that is definitely not the line (nor load) wire, but a travleler wire.   (after blowing the image up, it does in fact look like this is NOT the case and the black wire in the traveler connection certainly appears to correctly come from the traveler Romex; I cannot see where the actual Line/Load wire originates however) 

Ferinthul wrote

That will be the gang where i will install the 3-way... and i leave the "dummy" switch at the other gang. 

Well they are both 3-way - but I'm sure you mean the HS210 Smart Switch 

Incidentally (and I'm not nit-picking here - just to clarify) - many refer to that other switch as a 'dummy' - it's actually  a 'dumb' switch i.e. 'dumb' as in 'not smart' 

Dummy would imply it is not functionally being used for anything.