Worked... seems like issue while setting AWS secret key and access key.
Executed :
bin/elasticsearch-keystore remove s3.client.default.access_key
bin/elasticsearch-keystore remove s3.client.default.secret_key
bin/elasticsearch-keystore add s3.client.default.access_key
bin/elasticsearch-keystore add s3.client.default.secret_key
and
POST _nodes/reload_secure_settings
And it worked