I have WattOS R9 Microwatt, 64-bit, and I'm trying to boot a live USB on a Toshiba Satellite.

When I put in the live USB, the light on the USB stick comes on, because the boot order is set to look for the USB first, but instead of booting the live USB it goes straight to my normal Grub menu (Elementary OS and Windows 10). I've tried two different USB sticks, one of which I've used to create live USBs for other distros and never had a problem. I also tried creating the live USB in both Unetbootin and Universal USB Installer (choosing WattOS as the distro in the latter during creation of the USB).

I've run out of ideas as to what to try. Laptop doesn't have an optical drive. I could check out the distro in VMWare, but if I like it and want to install I'm not sure how to get around the USB issue. Thoughts?