YN-E3-RT won't link to 600-EX-RT

Is anyone having trouble getting the YN-E3-RT working? I bought 3 600-EX-RT's. I set one 600 to master, one to slave, matched the ID and channel, set in radio mode (not optical) and the master fires the slave no problem.

If I take the same slave, and set the same ID and channel on the E3-RT, it won't link with the 600 to fire it.

I've done the firmware upgrade to 1.10, new batteries, tried different channels, and yes, read the manuals. I've contacted YN, but have not heard back yet.

Has anyone else experienced this? I'm hoping I'm just missing something, and I didn't get a bad unit.

Probably your device is defective and must be replaced

The same problem: http://haodua.com/yong​nuo/yn-e3-rt/

Thanks. I was kind of afraid of that. Fortunately I got it off of Amazon, so the return process will be easy.