This KB describes the reason for that alarm to be raised on MIST Dashboard when manage a switch
Due to this alarm, changes cannot be saved and "Save" button will remain grayed out.
Unable to save changes on Mist Dashboard
This alarm is raised as a result of following configuration:
On which you are selecting as Source Address, the logical layer 3 interface configured for that specific vlan, but that layer 3 interface is configured to get its IP address through 'DHCP', instead of 'static':
Once that configuration is changed to static, and an IP address is configured, alarm will disappear and "Save" button will be enabled.