Just got a Z15 about two weeks ago and the thing won't turn on about half the time I boot my pc. It's in a USB 2.1 port, firmware fully up to date. I unplug it and plug it back in and it works everytime. Anyone else have this issue? 

I'd suggest plugging the keyboard into a different USB port or a USB 3.0 port. If you're using an AMD X570 motherboard there are known issues with the USB2.0 port in general. Also testing the keyboard on a different system to isolate it the keyboard and your system

Yeah, USB 2 ports won't cut it. Try a 3.x port instead - should improve things.
 
Just be aware that if you've programmed any custom color layers, you'll lose those going to another USB port. If you did and you don't want to re-program them all over again, let me know and I'll give you a quick run-through of how to recover them.

Very good, thank you both for the help

im going to try an evga z15 i should have it saturday from a logitech g413 so i hope i like it and price was good does anyone with z15 like it ok.

I personally never was a big fan of Logitech's RomerG switches on my G810 keyboard. I prefer the traditional mechanical switches either linear or tactile. The Z15 will let you find the switch type you like as long as the switches support SMD LEDs and are 3 pin (you can use 5 pin switches but will need to clip off the 2 extra legs)

I have had that happen with my z15, where it does not detect on start up, at least on my new pc. took unplugging and plugging it back in. Not having that issue with my z20 oddly. My z15 though works fine in my old eight year old pc.

I'm having this issue on INTEL mobo, asrock z590 steel legend. also it only happens with this keyboard. I was using a cheap mechanical keyboard without any issues and regular keyboards too

May want to check your mb bios USB settings either csm or legacy support for USB devices. 

alright I checked all the settings on bios and windows.
I switched my usb ports always usb from the mobo but problem keeps happening
Now I'm testing to plug the keyboard on USB 3.0 ports from a PCI-E card that I have installed on the PC
I feel like it's working better than before but on 1 time keyboard lights went off, but I was able to still use it.. but ALL the lights are off. even NUM LOCK and CAPS lights are off.
Also 1 time happend that the lights were all on but I wasnt able to use the keyboard.. like the keys didnt respond.
 
Now I'm thinking that it might be a bios issue with the mobo ports and the pci-e usb's don't have enough power for the keyboard?