Error was HTTPConnectionPool Max retries exceeded

we are using consul to register service name and version deployed on the server.
suddenly we getting below issue while registering service tag.
FAILED! => {“changed”: false, “failed”: true, “msg”: “Could not connect to consul agent at localhost:8500, error was HTTPConnectionPool(host=‘localhost’, port=8500): Max retries exceeded with url: /v1/kv/devenv/service-test (Caused by NewConnectionError(‘<urllib3.connection.HTTPConnection object at 0x7f733fa444w3>: Failed to establish a new connection: [Errno 111] Connection refused’,))”}