The "authentication failed" error message is often the result of one of five conditions.

• Password missing after copying connection string from the Atlas web page.  This is a security precaution, please enter the password manually in the Compass connection window.

• Username and password mismatch

• No user account exists in a new Atlas project under Clusters: Security: MongoDB Users

• Not specifying any or the correct "Authentication Database", (aka authSource), usually "admin" for Atlas clusters

• Selecting an incorrect "Authentication" method

原文：https://www.cnblogs.com/zergling9999/p/14769016.html