Unable to connect to Atlas via mongodb shell

i have crreated a sandbox cluster now i am trying to connect through mongoshell but getting error message.
Error: connect failed to replica set sandbox-shard-0/sandbox-shard-00-00-wff1x.mongodb.net:27017,sandbox-shard-00-01-wff1x.mongodb.net:27017,sandbox-shard-00-02-wff1x.mongodb.net:27017 :
connect@src/mongo/shell/mongo.js:251:13
@(connect):1:6
exception: connect failed

Connection string:
mongo “mongodb://sandbox-shard-00-00-wff1x.mongodb.net:27017,sandbox-shard-00-01-wff1x.mongodb.net:27017,sandbox-shard-00-02-wff1x.mongodb.net:27017/test?replicaSet=sandbox-shard-0” --authenticationDatabase admin --username m001-student

Is your sandbox cluster up and running?
Please check

2019-05-24T07:24:18.848+0530 W NETWORK [js] Unable to reach primary for set sandbox-shard-0
2019-05-24T07:24:18.849+0530 I NETWORK [js] Cannot reach any nodes for set sandbox-shard-0. Please check network connectivity and the status of the set. This has happened for 8 checks in a row.
2019-05-24T07:24:18.860+0530 E QUERY [js] Error: connect failed to replica set sandbox-shard-0/sandbox-shard-00-00-wff1x.mongodb.net:27017,sandbox-shard-00-01-wff1x.mongodb.net:27017,sandbox-shard-00-02-wff1x.mongodb.net:27017 :
connect@src/mongo/shell/mongo.js:328:13
@(connect):1:6
exception: connect failed

Thankyou Issue has been resolved already.