Opensearch serverless dashboard not visible. Giving HTTP error response 401

I have deployed opensearch serverless collection. The collection type is VectorSearch. I have also defined all the security policies, like data access policies, encryption policy (Using KMS key), Network policies. Since I want my collection to be private, I have defined private access type in my network policy and gave vpc endpoint id which I have created. Enabled access to OpenSearch endpoint and OpenSearch dashboard as well but when the collection is created and active and I am trying to hit the dashboard endpoint URL, it is giving me HTTP error response 401. I have been trying to troubleshoot this for the long time. I also have all the required permissions given for my IAM user. Still not being able to figure out what the issue is.