the kyocera E6782 remote: bootimage: incomplete or not signed

My kycera E6782 cant go into fastboot with twrp for 5.1.1 system ,for 4.4.2system is ok. but 5.1.1system not .
"remote: bootimage: incomplete or not signed''
pelease help ......

from xda-developers http://ift.tt/235OlNX
via IFTTT