A problem occurred whilst trying import Journey information (Opens, Clicks etc) from Campaign Monitor.The error may contain a the actual journey that we can't retrieve. It will look something like: J:4d1cd8e52b410cd37d36375e6e57s2a10 (there the number after the colon represents the internal Campaign Monitor Id for the journey). It's possible the journey Id is invalid (it may have been recently deleted or changed in Campaign Monitor).Check the associated log details in Maintenance for details on which custom trigger/process etc in Salesforce is causing the issue. Disable that custom trigger/process and then perform a Full sync (to ensure the email tracking history is correctly updated).There could also be a temporary maintenance outage with Campaign Monitor. If so, check the sync later.