Have you replaced the HCU/ABS unit? If not, then you do not need to bleed this. The valves are normally closed unless you are in an ABS event. So again, as long as this is not a new unit, it is most likely not the issue.
Did you bench bleed the master cylinder? If not, you have air trapped in the master cylinder. I attached the process on how to bench bleed the master cylinder which you can do installed on the vehicle. Then you will need to bleed the entire system again.
Let me know if this makes sense and we can go from there.
Images (Click to enlarge)
Monday, June 1st, 2020 AT 6:42 PM