1) always take before photos of the existing wiring including the screw attachments
We all think will remember how it was, but we won’t.
2) make no assumptions about what the wiring “must be”. there are at least eight different ways to hook up a three-way. There won’t even necessarily be a load line to the master. (Really)
Seriously, I know I say this a lot, but you can’t go online, find a diagram, and even if the colors match what’s in your box assume that that’s how your switches are wired.
You have to get a testing tool, and you have to test every segment of every line to figure out exactly what it’s doing. there are no shortcuts to this. No matter what you Google.
The Pretzel Express
With a non-networked switch think of the circuit as one big loop that has been cut in multiple places and twisted back into pretzel shapes. Now, the various switches, both masters and auxes, are stuck into the places where the line was cut. As long as there is some combination of the various Switches that lets current flow from The street to the light and back again, the light can come on.
Think about a toy train set. The kind where the train is running under electrical power and actually switches from one track to another. The train is running around the track. It’s the kind that requires you to manually push a button at each junction to switch the track. You can keep opening and closing different pieces, and as long as the train has some path to get to where it’s going, it won’t derail. And at any given moment there might be a part of the track that the train can’t get to it all, and that’s still OK. If you need to train to get there you switch the track to that section.
The active section might keep changing, and at any one moment some pretzel loop somewhere might be disconnected from the path train is on and not be receiving any current. That’s OK. It will still work. So you can have a big table and a couple of kids running around trying to manually switch the tracks before the train crashes.
That pattern does not work for a networked switch. The reason is that each switch control, instead of just being flipped by The person at that junction, gets its order to switch over the radio. That means it has to have power for the radio so it can hear the next command. And that means (this is the important part) that every part of every loop up to each switch has to have a little current in it at all times. You can cut off current past the point of the radio, but each radio has to have current.
I hope that analogy is clear, because it’s a really important concept. You are taking one of the old pretzel loops that had manual control switches and now you’re replacing it with radio control switches that need to have some current to every switch all the time. (But not necessarily the same level of current that the old switches used.)
That magical Internet drawing
If your particular current pattern was different then the guy Who drew the diagram you found on the Internet, the current may flow differently. So when you put in the new network switches, you might end up with no live current to the master. Or current that keeps getting shut off as the auxiliaries open and close.
You cannot do this work solely from a diagram.You can study the diagram to try to figure out where you want to end up. But you have to test the lines you have to know how the current is flowing in your original set up.
3) wire colors are not mandated in most US jurisdictions. People can and do just pull the last piece a wire out of the box at the end of the day and use it for anything. I’ve seen hotlines that were white wires, I’ve seen travelers that were black wires, I’ve seen switches that had four black lines coming into them and not one of them was a load line. The only way to know what you have is to to test every segment of every wire.
You may find a diagram that works perfectly for the upstairs hallway, but your kitchen turns out to be wired in a completely different flow pattern. Even if it looks exactly the same in the picture. They might reversed the colors that were used downstairs. Plus by some estimates based on time of sale inspections, about one third of US residential wiring is just done wrong. It’s not going to match anybody’s picture.
So there’s no one magic way to do GE switches, or any other kind of switches. At least not in the United States. You just have to work with the wiring that is in front of you. Every single time.
To be honest, the reason why we always take before pictures, is because there’s no telling what the previous guy did! Sometimes you just have to put it back the way it was to get things to work, with the old equipment, and then go all the way back to the circuit box and start working your way forward figure out what the heck is going on.
This is the main reason I don’t give wiring advice on individual set ups on the Internet. I can guess at what might be wrong based on the symptoms you’re saying, and suggest some possibilities to research, but I have no idea what’s actually running through the wires in the picture. And neither do you until you test them.
Your basic principle is very good. You want to start by getting the master switch working. And as @Navat604 often says, the new master will require both the hot and the load, so you have to find those. But depending on how the old switches were wired, honestly they could be anywhere in that big pretzel loop. It’s not about which one comes first. Which one comes first is often important in non-network switches. But once they’re networked , they all have to have some current all the time.
The difference in a networked setup between the master and the aux is that the master controls the load. And it may be that in the old nonnetworked switches the load came in at some random other spot but it worked because by the time the kids were finished running all around the table there was a clear path for the train. That approach does not work for networked switches. So quite often when you take out the nonnetworked three-way, and you put in a networked three-way, you do actually change the way the current flows through that circuit.
So figuring out where the master is going to go is absolutely the first step. And getting it working is absolutely the second step. But as far as what that’s going to look like, there’s no telling, and there’s going to be a lot of variation.
Just sayin’… 
