I'm having a problem booting a usb drive that contains High Sierra which I acquired by using a patcher from dosdude1. Can't boot from usb. Any advice?

[ozmuha]

I am attempting to upgrade a late 2011 Macbook Pro 13" from Mountain Lion to High Sierra or a more current OS if possible. I have used the awesome guidance from the dosdude1 website.
When I get to the point of trying to boot from the usb containing the HS os, using the option key to get in to boot choices, I see the usb drive, and HD, I select the usb which contains the HS that was loaded via the MacosHighSierraPatcher, and it bypasses my selection and boots into Mountain Lion.
I've tried to boot the usb 3 times to load high sierra. No luck. Does anyone have any suggestions on a workaround.

Thanks,
Ozier