Type: Configuration error (You are often able to resolve this type of error.)
Description: Wrong username or password.
Possible solution: Please enter a valid set of credentials. Check that the specified username and password can be used to log in to Exchange.
You can also check that username and password can be used to log in to your EWS URL (If you are using O365 the EWS URL will always be: https://outlook.office365.com/EWS/Exchange.asmx)
Furthermore, you can check if the service account can access EWS externally using the following Microsoft Connectivity Tool website: https://testconnectivity.microsoft.com/#&&Jtn0NnPPEC4GA7XXbfXtBsFMMpLP/1L9WRZephR4rWelHOpg2VRYAX7jbAcDJs4ZkdyCar8vg26eu7AkKZoYKtOM31mA5mwffO0Ze13OWZIryQ46PWeIbQB3OqBpKnvJl++a3peWGzuLYsJsGT+II2Uze06Yh2pDRKO3CtarEfKtDVl0HmxLhPN9JKIZe9pwmeaScw==