I believe we have established fairly conclusively that there is indeed a problem printing accurate targets using ACPU under mac OS X El Capitan (and perhaps Sierra). See post #8. Mark Segal has undertaken detailed and exhaustive printer testing and I would trust his conclusions. If you have made any profiles recently under El Capitan you might want to review and check them.
I was taking about Apple Colorsync Utility (ACU) not ACPU, but just to make sure ACU is still able to print correctly to the Pro-1 driver in "print as color target" mode, I just performed the following steps.
1) Checked my Pro-1 Firmware. It is up to date.
2). Checked my Pro-1 driver version. It was 184.108.40.206, which was not the latest, so I just updated today. It is now latest version 220.127.116.11
3) Sent untagged TC918 color target to printer, using "print as color target" in ACU and made sure all other media settings were correct and sticky (i.e. not defaulting to something else).
4). I just looked at the print which finished a few minutes ago. It is a correctly printed untagged, non color managed output! What more can I say, other than the fact that I've been making ICC profiles for 25 years, and over that time I have learned to recognize instantly whether the chosen color target has printed with color management truly turned off.
Only advice I can give at this point is to make sure printer driver and firmware are up to date. Also, even if up to date, uninstall the driver in Mac system preferences "printers and scanners" menu, restart computer then reinstall the driver. This step alone can sometimes fix Mac printing problems. Also take your target image into PS and recheck to make sure it is truly an untagged file. If not, PS can unembed any embedded profile. Then give ACU "print as color target" feature another try.