I had the same experience.
Just for testing purposes I left channel 1 at full intensity (255) and did the remaining instructions, red blinking, then white flash. It took a couple of tries but it did accept the 255 as the start channel. I found it easiest to then test with xlights. Do rgb light test, turn on all channels, top slider should be red, second green etc...then narrow down the channels (hopefully to 255r, 256g, 257b, 258w. At that point at least you know the aether is working correctly. I have yet to get the EXACT start channel I desire. But at least I know the aether build is good.
Got a DMX dongle on the way to solve the problem, hopefully.