You may notice the following error (something similar) in the event viewer where BizTalk 360 monitoring service is running. 

CreateMailActivity.TimerElapsed. Error. Exception:Login failed for user 'CORP\KOV006W2008R2$'.
Login failed for user 'CORP\KOV006W2008R2$'.

Make sure the service account is part of BizTalk Administrators group.


BizTalk monitoring services fetches data from all the configured underlying BizTalk Environments to generate alerts. Configured BizTalk environments will be accessed using the service account configured for the monitoring service.  So, its mandatory to make the service account part of each BizTalk Adminitrators group.

Ex: If you have configured 3 environments SIT, UAT and PROD. Then the service account must be part of BizTalk Administrators group in all the environments.