Intel NUC Could not mount LABEL=Storage

It's booting the kernel but the init script is not able to mount the squashfs SYSTEM file from the /flash (boot) partition. The normal reason is the filesystem being marked 'dirty' and it needs cleaning to boot normally. The less normal reason is corruption to the SYSTEM file which could be an early indicator of issues with the underlying storage media, e.g. the good thing about LE is the entire OS is contained in two files, but the bad thing about LE is the entire OS is contained in two files; corrupt either file and the OS doesn't boot (whereas a normal distro spread over several thousand files is more tolerant towards single-file failures). USB boot a desktop OS like Ubuntu and fsck the filesystems. If that's not the issue try dumping the 512MB boot partition using dd as that will attempt to read the data areas where the SYSTEM file is stored. The other reason this error shows up is the partition labels not being set, but if the box was already working that's rather unlikely (although discovering new stupidity with NUC firmware stopped being a surprise a long time ago).