I had to remove and add my 3 boosters yesterday. When re adding the first hardwired booster, I was prompted to join its network, which I did. When adding the second booster, I had to switch to my newly created wifiplus3384 network rather than my t3200 network.
I app is quite buggy, but i found a workaround where cancelling the process and readding the boosters, in sequence I might add, (2 of my boosters share the same SSID) wifiplus3384, wifiplus3384, wifiplus3228.
I hope that helps