Use serverless-plugin-aws-alerts plugin with existing SNS Topic

Serverless Framework
,
1

I’m trying to set up email alerts for my Lambda errors (…invocations, etc). I can update my .yml file to create a new topic and this works OK:

custom:
  alerts:
    stages:
      - production
      - dev
      - development
    dashboards: true
    topics:
      alarm:
        topic: ${self:service}-${sls:stage}-alerts-alarm
        notifications:
          - protocol: email
            endpoint: myemail@domain.com
    alarms:
      - functionErrors
      - functionThrottles
      - functionInvocations
      - functionDuration

I receive emails as expected.

But when I try to use an existing SNS Topic, by following the SLS docs, nothing seems to happen. I’ve:

  1. Created a Topic in the SNS console
  2. Updated the .yml as per the docs:
custom:
  alerts:
    stages:
      - production
      - dev
      - development
    topics:
      alarm:
        topic: arn:aws:sns:${aws:region}:${aws:accountId}:myp-${sls:stage}-alerts
    alarms:
      - functionErrors
      - functionThrottles
      - functionInvocations
      - functionDuration

The deploy works fine, but I don’t get any emails when I trigger errors. What do I need to do?