GTM Config Sync not working

I know this is an old issue but for anyone who might run into this in the future I had this same problem. After reviewing logs for /var/log/gtm on both gtm devices I noticed a recurring error that turned out to be an improperly named wideip someone had created that was preventing sync from completing properly. Deleted that wideip and everything was fine after. So it's definitely worth checking out logs and looking for weird things in your config.