Can't load Windows 10 in Bootcamp
I am following the Apple guidelines installing Windows 10 (1st time install, not an update) on my late 2015 Retina 5k iMac (with Fusion Drive) and it's not getting past the "format" step within the Windows setup portion of the bootcamp partition. According to Apple, this Mac should work with Windows 10. Below is a picture prior hitting format. I assume I choose the partition titled Bootcamp (which BTW, shows 280GB although I chose 300GB when I selected the partition size at the beginning of Bootcamp) and then, as indicated below, since it can't be installed there until formated, I hit the Format button as instructed.
It only "formats" for a few seconds and then the following drives show up and the Bootcamp is missing next to Drive 0 Partition 5. If I then select Next, the message shows up as seen at the bottom of the screenshot. It won't go forward from here and I have to exit out. The extra 300GB partition remains on my Mac when I go into Disk Utility again but Bootcamp is removed as its name. It's called Untitled.
I've called Apple Care and they tried to help by sending me the bootcamp instructions from about 3 versions of OSX ago, saying it should be the same. Clearly not...the under the new El Capitan process, you can use an ISO file on the Mac versus a USB stick, among other things. Funny that my iMac isn't listed as one than can use the local ISO file versus the USB stick, but when i mentioned that to Apple Care, they didn't see to know about the list of compatible Macs for that purpose. I asked if there was another way to try versus the local ISO file and thats when they sent me the old bootcamp instructions. Then they then said it was a Windows problem since I was inside the Windows setup process when all this occurred. Called then for a good laugh and they immediately said it was an Apple Bootcamp issue and wished me good luck. Big surprise.
On other walk through instructions I see online, it follows these same steps but I do notice that there are not any other Drives in the window to choose from (like Drive 1, Drive 2, etc.) I don't have any Thunderbolt drives, which Apple suggest gives this error message. I've also unmounted any other USB drivers when I've tried all this.
Any suggestions would be helpful. I have screenshot at almost all the steps along the way, but I think the root of the issue is when it gets to this spot.
