what can i say.... the PS4 is just REALLY REALLY PICKY
you might want to gather all the usb flash drives you can find at home, and have a whole afternoon free, before attempting replacing your ps4 hdd. having ps plus helps, so u can restore saved files from the network.
tried 2 sony 16gb usb sticks, didnt work, tried various things, exFAT, FAT32, win7, winxp, partition magic, freeware formatting programs, left and right usb ports, usb hubs, usb extension cables etc....
tried data traveller usb 8gb didnt work either.
used the PS3 GAMEGENIE usb stick (oops!) which was formatted in FAT, not FAT32. in right usb port of a UK PS4. worked flawlessly.
its a 1GB stick, so maybe smaller sized drives will increase the chance of success (even though some people have reported that a 16GB usb did work for them)
if u get error 30774-1 it means your usb is fine, but the update file is missing, wrong, or wrongly named.