Nightscout - Boot Error

Unable to setup authorization
    {"stack":"MongoError: not master and slaveOk=false
    at /app/node_modules/mongodb-core/lib/connection/pool.js:581:63
    at authenticateStragglers (/app/node_modules/mongodb-core/lib/connection/pool.js:504:16)
    at Connection.messageHandler (/app/node_modules/mongodb-core/lib/connection/pool.js:540:5)
    at emitMessageHandler (/app/node_modules/mongodb-core/lib/connection/connection.js:310:10)
    at Socket. (/app/node_modules/mongodb-core/lib/connection/connection.js:453:17)
    at Socket.emit (events.js:198:13)
    at addChunk (_stream_readable.js:288:12)
    at readableAddChunk (_stream_readable.js:269:11)
    at Socket.Readable.push (_stream_readable.js:224:10)
    at TCP.onStreamRead [as onread] (internal/stream_base_commons.js:94:17)","message":"not master and slaveOk=false","operationTime":"6794940902847545345","ok":0,"errmsg":"not master and slaveOk=false","code":13435,"codeName":"NotMasterNoSlaveOk","$clusterTime":{"clusterTime":"6794940902847545345","signature":{"hash":"yZOUGDngvxoDvSZbxUCoS70SLWY=","keyId":"6762709853350658050"}},"name":"MongoError"}