This is what I get when I try to flash via fastboot
fastboot.exe flash zip cm-11-20140823-NIGHTLY-t6spr.zip
sending 'zip' (231234 KB)...
OKAY [ 10.957s]
writing 'zip'...
FAILED (remote: not allowed)
finished. total time: 10.992s
Via recovery I get an error indicating install failed and it just aborts. I can try again an send you the exact message