Sync with Rainlendar only oneway function

[Dan-cer]

Yesterday I regarded that syncing from Rainlendar to Zimbra calendar doesn't take place. The other direction is syncing. All tasks and events created in Zimbra are shown in Rainlendar.

But if I create a new task or event on rainlendar, there will be no syncing. After starting zimbra in browser, the new items in rainlendar are deleted.

Syncing on smartphone using Microsoft Exchange ActiveSync is working in both directions.

Any idea why one way doesn't sync with rainlendar?

In the past - I remember - both directions were working.

Thank You for Your answer!