I guess it is an issue with the awsmobile config object, can you try adding the following keys?
"aws_appsync_graphqlEndpoint": "https://your.appsync-api.ap-south-1.amazonaws.com/graphql",
"aws_appsync_region": "ap-south-1",
"aws_appsync_authenticationType": "AMAZON_COGNITO_USER_POOLS"