You should check that your /EFI/OC/Drivers folder contains OpenHfsPlus.efi or HfsPlus.efi, as without one of these two drivers your system won't see any HFS+ drives on the GUI boot screen or Picker list.
HfsPlus.efi is the better of the two drivers, while OpenHfsPlus.efi usually comes as part of the OC EFI contents.
The driver has to be enabled in the config.plist as well as being present in the Drivers folder for it to work.