You can find the same question [here][1] I just encountered this error:
Server is running on port: 5000
MongoServerError: bad auth : Authentication failed.
at Connection.onMessage (/home/mostafa/documents/local-repositories/mern-mongodb-tutorial/server/node_modules/mongodb/lib/cmap/connection.js:202:30)
at MessageStream.<anonymous> (/home/mostafa/documents/local-repositories/mern-mongodb-tutorial/server/node_modules/mongodb/lib/cmap/connection.js:62:60)
at MessageStream.emit (node:events:527:28)
at processIncomingData (/home/mostafa/documents/local-repositories/mern-mongodb-tutorial/server/node_modules/mongodb/lib/cmap/message_stream.js:108:16)
at MessageStream._write (/home/mostafa/documents/local-repositories/mern-mongodb-tutorial/server/node_modules/mongodb/lib/cmap/message_stream.js:28:9)