Check your i3 devices to ensure the RF Channel is enabled.

[TahoeJimbo]

TL;DR: You should check your i3 devices to ensure the radio band (the primary way Insteon communicates) is enabled. With the exception of the on/off outlets, you can do this in the Admin Console. For outlets you need to factory reset your outlets. Use the beacon mode (four taps) to test if your i3 device is working properly.

This post has been updated to include all i3 devices. Thanks to paulbates for his addition.

Deets:

I installed then linked a few of the new-ish i3 on/off outlets (v.54) into eisy via my USB PLM.

The eisy had problems talking to all of them... The linking process took around a minute to finish. The eisy continued to have issues. Commands would outright fail after a couple attempts.

I put one of the outlets into RF beacon mode (four button taps) and NONE of the nearby Insteon devices responded. Nothing. Nada.

This happened with all three of the outlets, straight out of the box.

I did a factory reset on each, then relinked with eisy without problems. Now they work great, and beacon mode now causes all the nearby devices to respond.

For other i3 devices you can check that the RF channel is enabled using the Admin Console by checking the option flags as outlined in Paul's comment below.

Things I learned:

1. It appears that the primary radio channel wasn't enabled "out of the box" which forced the backup channel into service.
2. My house has serious issues with power line noise that messes with the backup channel. The PLM was trying hard to break through the noise, but had a hard time.
3. Bonus Thing!: The command strings needed to control Insteon outlets are much longer (22 and 23 bytes) which makes them more susceptible to being nuked by noise on the backup channel. (For comparison, dimmer commands are 8 and 9 bytes.)

So there you have it. If you have an i3 device, try beacon mode or check in the Admin Console to see if the radio channel is actually working.

Edited May 7 by TahoeJimbo
Update to include all i3 devices.

[paulbates]

Thanks..  One of two of my outlets turned out to fail the 4 tap test too.

I went on to "4 tap test" my i3 paddles. 2 of 11 Paddles exhibited this same behavior, not responding to the 4 tap. I looked at the i3 flags for each. There's an option/flag for turning off RF (??) and it was set to on- they weren't using rf!! 

I had to factory reset the i3 paddles to get it to work. I would add to your post that its worth going through all of the i3 flags, doing a query for each one to see what's what.. it was a surprise for me. They had been functioning just fine this way, this particular device is the furthest away from the panel in wire feet.

The i3 outlet doesn't have the flags, so the reset is needed

Edited May 7 by paulbates
Had to reset the i3 paddles anyway

[someguy]

Thank you guys both so much for posting this info!!!  I just got a new i3 outletlink and it had the same problem and it was fixed by the factory reset as you suggested.  Thank you and kudos!!!!!😀