Items do not appear on mobile devices synchronized by ActiveSync service
You have enabled the synchronization in CodeTwo Exchange Sync product. On desktop clients you are able to see that the data is being synchronized. However, on the mobile devices connecting via ActiveSync you do not see the items.
First of all, make sure that the synchronization actually works. To do so, please open problematic mailbox using Outlook Web Access (OWA) and check if items are synchronized. If you do not see your items, most probably the synchronization is down and you have to troubleshoot this issue first, as per this article.
If you are sure that your synchronization works properly, the problem may be related directly to the behavior of ActiveSync. CodeTwo software does not use any email client to work nor it accesses mobile devices or client computers - it processes your items directly on the Exchange server, using MAPI libraries.
Since you confirmed that the content of mailboxes is updated properly by CodeTwo Exchange Sync directly in Exchange mailboxes, the problem you are facing, is the synchronization between your mobile device and the server. This kind of synchronization is done by Microsoft ActiveSync on Exchange Server and there is no chance that our software would interrupt the entire process.
However, when only particular items are not visible, check whether they are synchronized by CodeTwo Exchange Sync software and what modificators you are using in your synchronization task - perhaps using one of them is causing the process to fail. If you are sure the problematic items are always synchronized by our product, consult this problem with CodeTwo Customer Service.
Although, in the case you do not see any item on your mobile device, we would recommend to open a support ticket with Microsoft, as the issue seems to be related directly to ActiveSync.