When you try to add a SharePoint library manually (see Add additional document libraries), you get the the error message "Failed to open site: Key not found".
Error-Message: "Failed to open site: Key not found"
Microsoft (temporarily) changed the content of the response of the query for the library discovery for some tenants. Therefore KONNEKT will not map those affected libraries.
Solution
We implemented a workaround for that behavior starting with KONNEKT V2.0.0. Please see here, how to get the update: Software updates.