Does anyone know how I can create an alert when a link in a PortChannel goes down?
You need to enable monitoring on the individual interfaces in the port channel as well as the PCh itself. Then they will alert based on your interface alerts.
e.g. if we have G1/1 and G2/1 in a Port-Channel1 then we would monito all 3 interfaces - 2 physical and 1 virtual - as an interface. Just select them via List Resources.
Also in Maps, if you use it, between the two devices you can connect them or draw a line and right click and drop the port channel interface ie in Cisco Po1 or aruba lag1 into the link line between the devices
If you are after the actual alert - this is the SWQL from one we use
SELECT E0.[Uri], E0.[DisplayName]FROM Orion.NPM.Interfaces AS E0 WHERE ( ( E0.[IfName] LIKE 'Po%' ) AND ( E0.[Status] = '2' ) )
So this is for a Cisco Port channel when it loses a member.