There could be an occasion where the criteria in your policy block is met, but the action to send out an email alert is not executed.
If your policy block is scheduled to evaluate around 3:30AM PST please try changing the policy block to run 1 hour before or 1 hour after this time. Jobs that run at 3:30AM PST are running at peak times at which we have a lot of policies being executed, which could be the reason why alert emails in your policy block were not sent out.