Сannot sync file for several months

The inability to remote sync to a single bay My Cloud with third party software is one of the problems with using any software other than WD Sync. Free File Sync does support syncing remotely using SFTP. There are ways to possibly use SFTP on a single bay My Cloud that have been discussed in other posts.

https://community.wd.com/search?q=SFT%20category%3A105

Another option that may work for remote syncing is GoodSync: