My previous Mini-ITX DIY Hackintosh gave up the ghost about a week ago; could not even get into the BIOS. So I bought and installed a new GA-H170N-WIFI motherboard with an Intel Core i7 6700 CPU and 16 GB Kingston DDR4 RAM. Used my Unibeast v6.2.0 flash drive and installed El Capitan on my Samsung 840 EVO SSD "SSD1." Chose SSD1 to restart after the installer completed, and got the subject response. I tried the "Boot0 Error" routine published on tonymacx86.com about 2 years ago, but Terminal...
"GPT - Test - Test - Test - boot0"
"GPT - Test - Test - Test - boot0"