Not sure if this is known, as I'm a new Kaseya user, but I spent a few hours chasing this down with Cisco support, so I thought I would share.
If you are using Cisco Umbrella, with Intelligent Proxy they are currently grey listing mbamupdates.com which will result in KAM not updating. You need to disable Intelligent Proxy in Umbrella or whitelist mbamupdates.com
Cisco support is working on the issue now, so they claim.
Support got back to me and let me know they had determined it was a false positive and whitelisted it.