cross account SNS topic publish - amazon-cloudwatch

Question

I have an SNS topic in account A that takes an error and sends to pager duty
I have another account - Account B that has several services in it, fargate, SQS etc but I have several cloudwatch alarms / actions setup to publish alerts to this SNS topic in account A
I get this error on Account B (the one trying to access the cross account service)
Failed to execute action
arn:aws:ACCOUNT-A:sns-topic.
Received error: "Resource:
arn:aws:cloudwatch:ACCOUNT-B
is not authorized to perform: SNS:Publish on resource:
ACCOUNT-A:sns"
here is my AWS CDK code for Account A
const accountATopic= new sns.Topic(this, 'accountATopic', {
displayName: 'accountATopic'
});
accountATopic.addSubscription(new snsSubscriptions.UrlSubscription('Externalurl'));
accountATopic.grantPublish(new iam.AccountPrincipal('ACCOUNTB'));
and then in ACCOUNT B (not showing the alarms)
const ACCOUNTBTopic = sns.Topic.fromTopicArn(this, 'ACCOUNTBTopic ', 'ACCOUNT-A-ARN');
const action = new cloudwatchActions.SnsAction(ACCOUNTBTopic );
ACCOUNTBTopic .addToResourcePolicy(new PolicyStatement({
resources: ['ACCOUNT-A-ARN'],
actions: ['SNS:Publish'],
effect: Effect.ALLOW,
}))

Answer 1

For anyone that comes across this in the future - here is what I did to get it working:
const accountATopic= new sns.Topic(this, 'accountATopic', {
displayName: 'accountATopic'
});
accountATopic.addSubscription(new snsSubscriptions.UrlSubscription('Externalurl'));
let snsPolicy = new PolicyStatement({effect:Effect.ALLOW,
resources:[accountATopic.topicArn],
actions:["SNS:Publish"],
principals:[
new AccountPrincipal('ACCOUNTB_ID'),
]
})
//or optionally:
//snsPolicy.addAnyPrincipal()
accountATopic.addToResourcePolicy(snsPolicy)
The grant publish method does not seem to allow it to work, also according to AWS documentation on cross account SNS / CloudWatch they suggested adding the org id for a condition - this did not work for me and had to remove it