You might be super upset that one of your favorite features is not tracking the proposal activity all of a sudden. Let's not get discouraged!
First, check if you have accidentally used your login email address to test Customer Email. It's easy to see either:
On the Customer page of the proposal and presented proposal details
or
Inside the Event Log itself under "Emailed"
If you've send a proposal to an email associated with an Admin or Consultant user of OnCall Air, it will not appear in the Event Log.
As soon as you try to email to another address not associated with a user for your account you will should see the activity.