Unable to subscribe SNS to private API GW endpoint - not getting the subscription confirmation message

Serverless Framework
1

Can anyone please help me out? I am trying to subscribe SNS to private API GW endpoint. Unfortunately I can’t get the subscription confirmation message through. My serverless config should be correct, I even made it more permissive and still nothing. Can you please check the config and see if I am doing anything wrong (I only posted the relevant bits):

custom:
    url: "https://#{ApiGatewayRestApi}-#{TriggerVPCEndpoint}.execute-api.${self:provider.region}.amazonaws.com/${self:provider.stage}"
provider:
  endpointType: PRIVATE
  vpcEndpointIds:
    - !Ref TriggerVPCEndpoint
  vpc:
    securityGroupIds:
      - ${opt:vpcSecurityGroupId}
    subnetIds:
      - ${opt:vpcPrivateSubnet1}
      - ${opt:vpcPrivateSubnet2}
  resourcePolicy:
    - Effect: Allow
      Principal: '*'
      Action: execute-api:Invoke
      Resource: arn:aws:execute-api:*

functions:
  func1:
    name: ${self:service}-${self:provider.stage}-func1
    handler: src/handlers/func.handler
    timeout: 29
    events:
      - http:
          path: somepath
          method: post

resources:
  Resources:
      TriggerVPCEndpoint:
        Type: AWS::EC2::VPCEndpoint
        Properties:
          PolicyDocument:
            Version: "2012-10-17"
            Statement:
              - Effect: Allow
                Principal: "*"
                Action: execute-api:Invoke
                Resource: arn:aws:execute-api:${self:provider.region}:#{AWS::AccountId}:*
          ServiceName: com.amazonaws.${self:provider.region}.execute-api
          SubnetIds: ${self:provider.vpc.subnetIds}
          VpcEndpointType: Interface
          VpcId: ${opt:vpcId}
      TriggerSNS:
        Type: AWS::SNS::Topic
        Properties:
          TopicName: topicName
          Subscription:
              # url = "https://#{ApiGatewayRestApi}-#{TriggerVPCEndpoint}.execute-api.${self:provider.region}.amazonaws.com/${self:provider.stage}"
            - Endpoint: ${self:custom.url}/somepath
              Protocol: https

I even tried requesting the confirmation again via console and still nothing.