Alarm Condition Reference Not Found

For this alarm condition expression:
if(dateDiff({[.]execution p1_execution.LastChange},now(),“hour”)>24,1,0)

I’m getting the following tag alarm diagnostic error:
“activeCondition The reference ‘[.]execution p1_execution.LastChange’ could not be located. ERROR”

I tried using tag() in the expression as well.

Any ideas for what is causing alarm?