Resolved Issue: I ended up discovering the cause of my problem after waiting for Apple Support which was of no help. The issue turned out to be caused by having multiple merchant id certs loaded in my key chain then downloading the .p12 that was needed for the merchant id I was requesting the validation for. To correct the issue, I had to do one merchant id at a time by removing all other merchant id certs from the key chain but the one I needed the .p12 for. After taking those steps, my problem went away and the validation is working as expected. I hope this helps those who may be experiencing the same issue.