@Eli Ofek I double checked our Azure Network Security Group setup and the appropriate access is open. I also tested connecting to UDP 137 from our DCs using the Test-Port.ps1 Powershell script and it returned Open = True. 


We do have 2 Linux firewalls in the environment but I don't believe AATP even knows that they exist.  UDP 137 access was already open from the DC subnet however name resolution wasn't working.  I temporarily patched the hosts file on the DCs and will see if the health warning returns tomorrow.


Do you have any other ideas?  The message states the sensors are having 'low success rates'.  Is there a log somewhere that specifies which system(s) the sensors are having issues connecting to?  Is it the same message if the sensors can't connect to a single server vs. multiple/all servers?


Thanks again for your input!