USB backup device failed to mount: cannot proceed

[Spxi]

Hi I'm getting this issue when trying to install Linux onto my Dell Chromebook 3100 2in1
it shows my USB stink and everything but when I press 1 it gives me the error "USB backup device failed to mount: cannot proceed"

[MrChromebox]

it means that the first partition on the drive isn't mountable or writable. the script isn't smart enough to handle USB sticks/drives with multiple partitions.