AWS CloudFormation Fn::ImportValue doesn't like !Join? - aws-cloudformation

Question

I have the following resource in my CloudFormation template that's trying to create a listener rule. The idea is, based on the passed-in EnvironmentType, and the AWS Region, I want to import the listener ARN from the appropriate CloudFormation stack that exported it.
Parameters:
EnvironmentType:
Type: String
Default: "sandbox"
ECSClusterStackNameParameter:
Type: String
Default: "ECS-US-Sandbox"
Mappings:
production:
us-east-1:
stackWithAlbListenerInfo: "ECS-US-Prod"
eu-north-1:
stackWithAlbListenerInfo: "ECS-EU-Prod"
staging:
us-east-1:
stackWithAlbListenerInfo: "ECS-US-Staging"
eu-north-1:
stackWithAlbListenerInfo: ""
sandbox:
us-east-1:
stackWithAlbListenerInfo: "ECS-US-Sandbox"
eu-north-1:
stackWithAlbListenerInfo: ""
Conditions:
StackExists:
!Not [ !Equals [ !FindInMap [ !Ref EnvironmentType, !Ref "AWS::Region", stackWithAlbListenerInfo ], ""] ]
Resources:
AlbListenerRule:
Type: AWS::ElasticLoadBalancingV2::ListenerRule
Condition: UseListenerRule
Properties:
ListenerArn:
!If
- StackExists
-
- Fn::ImportValue:
!Join
- "-"
- - !FindInMap [ !Ref EnvironmentType, !Ref "AWS::Region", stackWithAlbListenerInfo ]
- "ListenerArn"
- Fn::ImportValue:
- !Sub "${ECSClusterStackNameParameter}-ListenerArn"
However, it fails validation due to this error, and seems like the first Fn::ImportValue: doesn't like the !Join. But !Join returns a concatenated string correct? What am I missing?
ERROR: Service: marcom-stats-service, cfnUpdate error: com.amazonaws.services.cloudformation.model.AmazonCloudFormationException: Template error: the attribute in Fn::ImportValue must be a string or a function that returns a string (Service: AmazonCloudFormation; Status Code: 400; Error Code: ValidationError; Request ID: 2678552e-cf6c-46e1-b640-a7c07de385c2; Proxy: null)
UPDATE:
Though Robert Kossendey's answer fixed my error, my original template was wrong. This is really what I wanted to do. I hope it helps someone.
AlbListenerRule:
Type: AWS::ElasticLoadBalancingV2::ListenerRule
Condition: UseListenerRule
Properties:
ListenerArn:
Fn::ImportValue: !Sub
- ${StackName}-ListenerArn
- { StackName: !If [ StackExists, !FindInMap [ !Ref EnvironmentType, !Ref "AWS::Region", stackWithAlbListenerInfo ], !Ref ECSClusterStackNameParameter ] }

Answer 1

Now I see it I think. At the second import you need to remove the dash in front of the !Sub:
- Fn::ImportValue:
!Sub "${ECSClusterStackNameParameter}-ListenerArn"