Moving to correct forum.
I have moved this post to the Lightroom Mobile forum. The File Hosting, Syncing and Collaboration forum is for issues with the desktop file syncing that is part of the Creative Cloud desktop application and the CC Assets site at https://assets.adobe.com.
One should not use the CC Assets site for backing up Lightroom catalogs. From the Lightroom and Creative Cloud FAQ at https://helpx.adobe.com/lightroom/kb/lightroom-creative-cloud-faq.html#id_9994
Can I store my Lightroom catalog in the 20 GB of storage space I get with my Creative Cloud membership?
No, you cannot store Lightroom catalogs in the Creative Cloud, nor can you save a Lightroom catalog on a networked drive. You must store Lightroom catalogs on your computer or on a locally connected hard drive.