Employee Grievance Handling?

I raised a grievance about the way my promotion was being handled after admitting that I was deserving of a promotion and there being a vacancy as well since 6 months. My boss had given me excuses for delaying my promotion for the third time by giving a reason which I told him was directly in contradiction with the company policy document. He told me that a promotion can only be given in March since it is linked to the appraisal process. The policy document categorically said it wasn’t linked to the appraisal process. He said promotions have to be approved by VP, CHRO and CEO. The document said manager level and below promotions are only approved by Senior GM (not even VP) and that’s it. Seeing dishonesty on his part and also perceiving racial discrimination since he is from the majority nationality in this company, I complained to the head office as per the grievance policy. Following acknowledgement of my grievance email , after a month and half, and that too upon my following up, I was emailed a one-liner by the Senior HR Director for the group saying that a panel looked into my grievance and found no violation of company policy or value. I am not satisfied with this one-liner of a reply and was hoping for a little bit of explanation like clearly at least saying that indeed promotions are only given in March and that they have to be approved by even CHRO and CEO!. How, if at all can I reply to this email? Also, the Senior HR Director who headed the investigation is himself from the majority nationality here. I don’t know if the panel that he says looked into the grievance reflected any diversity. How can I raise this issue and with whom…?