Thanks for the multiple replies. I've followed the advice given. I've performed a factory reset on the switches to remove the manually created links. While not mentioned, I also deleted the switches from the ISY controller and then relinked them so that I have a "clean" installation. Then I created a new scene listing both switches as controllers. The effort seems to be successful in that I now have a working 3-way circuit. Either switch will control the set of overhead lights and the LEDs on both switches are synchronized -- either all on or all off.
With all of the above working as expected, I'm experiencing an unexpected result. On one of the circuits I've setup, I'd like the two switches/controllers to function differently. When switched on from "Switch A" I'd like the lights to go to 100%. When "Switch B" is switched on, I'd like the lights to go on to a lesser amount...say 20%. I believe I've set this up properly in the controller (see attached screenshot). Let me try to describe what is happening. After the factory reset (but before linking to the controller), one of the switches controls the bank of lights while the other does nothing. On the Admin tool, I've marked this "master switch" with an asterisk. After linking the switches to the ISY controller and setting up the scene in the controller, whatever On Level I set for the master switch seems to control both switches. The attached screenshot shows the result. The "MBR Hallway MBR" switch is set with an On Level of 100%. When I manually switch on the lights from either switch, the lights go on to 100%. If I reverse the settings (MBR Hallway MBR to 20%), then both switches turn on the lights to 20%. In other words, the On Level selected for the "slave switch" seems to have no effect.
Any thoughts on the issue? I had the switches professionally installed by someone who isn't familiar with Insteon. Is this a problem with how the switches were wired? Something else? Again, thanks for the help. I'm trying to gain a basic understanding before I try more complicated scenes and programs.