Calendar Interop error messages & codes

Here's how to troubleshoot different errors you might get when using Calendar Interop.

Error messages  |  Error codes

Error messages

Error message	Details & troubleshooting
Connection error	Google Calendar can't connect to the Exchange server. A firewall might be blocking access. Or, you entered the wrong host name or port. To verify if the Exchange server is reachable from the internet, use Microsoft Remote Connectivity Analyzer.
Exchange Web Services (EWS) communication error	The Exchange server URL is using HTTP rather than HTTPS. HTTP is not a secure protocol. Specify HTTPS in the Exchange server URL.
EWS response error	Google servers aren't communicating with EWS but are connecting to another service (for example, a non-Exchange HTTP server). Common causes of this error include: You entered the wrong URL for the Exchange server. You entered incorrect Exchange credentials. There's a firewall preventing Calendar from connecting to the EWS server. In this case, make sure the EWS port is accessible from the internet. To find the correct URL for the Exchange server, in Exchange 2016, go to Exchange admin centerserversvirtual directoriesdouble-click EWS. For more information, refer to Synchronization, Notification, Availability, and Automatic Replies in Microsoft Remote Connectivity Analyzer.
Exchange username is not an email address	The Exchange username specified in the Google Admin console isn't a valid email address. For example, it might be missing the domain name. Verify that the Exchange role accounts use the correct email address.
Host not found	The DNS name is incorrect or misspelled. Or, there's no DNS record for the specified host name. Make sure the Exchange URL in the Admin console is correct. For details, go to Step 5: Set up the Admin console.
Interop is not set up	No Exchange connection settings were found. Calendar Interop might not be set up in the Google Admin console. Make sure Calendar Interop is turned on in the Admin console. For details, go to Step 5: Set up the Admin console.
Invalid attendee	The user you're doing an availability lookup for doesn't exist. Verify the user exists in Microsoft Active Directory.
Malformed Exchange URL	The Google Admin console doesn't recognize the Exchange URL. It might be in the wrong format. Check the settings in the Admin console and make sure the correct URL is entered. For details, go to Step 5: Set up the Admin console.
SSL error	The SSL certificate doesn't match the name of the host you're trying to connect to or it's invalid: You might have entered an IP address instead of a host name. Or, the host tried to connect using an alias that's not recognized by the certificate. If the certificate is invalid, it might be expired. Alternatively, it's from an untrusted root Certificate Authority. Make sure the SSL certificate on the Exchange server is valid and matches the name of the host you’re trying to connect to.

Error codes

Error code & name	Details & troubleshooting
400 Bad Request	Make sure the application ID is correct and retry. Check the settings in the Admin console and make sure the correct ID is entered. For details, go to Step 5: Set up the Admin console.
401 Unauthorized	Possible causes of this error are: Wrong value used for the client secret. An app registration might not have an associated client secret. Your organization’s Access Control List (ACL) might be blocking Calendar Interop. Check you correctly followed the steps in 2. Allow Calendar users to see Exchange availability and retry.

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