Since version 15.0 it is only possible to use five outputs for full support. If you connect/configure six or more all the leds turn off if you select white color. Everything else seems to be working fine.
I only have SK6812 leds, so I can't test if other types of leds show the same result.
My momentary solution is to use version 14.4.
I also tried the newest test-release that's available, but got the same result.
The solution I hope for is that in future releases the behavior is again acting like version 14.4.
Maybe I'm missing something and this is just the expected behavior, that would make me a bit down.