Cannot Connect to the Instance Default
One or more of the following conditions may be the cause of this error:
The log on account that the CES service uses has changed.
The password or the username that was specified for the CES service when CES was installed may have changed. When the password of this account changes in Active Directory, you must also manually change the log on information for the CES service on the Coveo server (see Modifying the CES Log On Account).
Note: A best practice is to create a user account dedicated to the CES service with a password that does not change, or does not change frequently (see About the CES Service Logon Account).
The account with which you logged in to the Coveo server does not have administrator rights.
Log on to the Coveo server with an account that has administrative rights and try again.
The CES service is not started.
The CES service does not start when either of the previous conditions occur. Ensure to fix them when needed, and then start the CES service (see Starting the CES Service).