Hi Jason,
Which DMM/SNS software versions are you running? There is a known defect on 5.3.6 that could be causing the error you are seeing:
CSCuf17696 - DMM-SNS - HA setup errors out with CSYNC error
Best option in any case is that you open a TAC case to get assistance on this and confirm if your issue is matching this defect or some other issues (misconfigurations etc.) might apply.
Regards,
Marco