That log line is not directly related to out-of-sync items. This means that you pressed the ignore button on the folder share banner in the UI for that folder, therefore the repeat “invitation” by that device is being ignored. AFAIK there is not yet a way to undo that in the UI. You can edit your config.xml though, to stop ignoring that folder.
On the list of out of sync (or failed) items in the expanded folder there should be a reason, why they aren’t in sync.