Provisioning Agent status
Each system configured to use an On-premises Provisioning Agent displays current Agent availability next to the 
The green dot indicates the number of on-premises Provisioning Agent instances which are currently active, and the yellow dot indicates the number which have been inactive for more than two minutes.
When no instances are available, a warning is shown:
In particular, this may happen when you have more than four on-premises Provisioning Agent instances installed and you have Microsoft Exchange integration enabled for Active Directory (due to Exchange session limits).