AppSync synchronize the schema with salesforce graphQL

Hi I'm trying to connect to appsync with salesforce using GrapQL connector in salesforce. I have setup appsync API with schema reading from my dynamoDB table. All works fine in AWS console using queries etc... I have also configured in Salesforce Named and external credentials and all seems to work ok but when I'm trying to Validate and Sync in salesforce (External Data Source) I've got Status=Success but no objects/tables (schema )are visible/sync. In cloudwatch i can see that api call has been made with IntrospectionQuery (Resolver Count 0, but I think this is ok as this is Introspection queries, FYI: Introspection queries is on ). I would appreciate any help. Thanks