iCloud Documents folder not syncing

Earlier this week my Mac's iCloud Document folder stopped syncing. I've reinstalled, restored from time machine, but it's still not syncing. I can still view everything on iCloud.com and iPhone, also web upload is working on safari browser.

Issue 1:

Documents folder not uploading to iCloud, nothing being uploaded after 24-48 hours.

Issue 2:

After reinstall, document folder is not downloading from iCloud. iCloud document/desktop folder option is already enabled.

Apple support has already escalated this to Engineer level. Not sure what is the cause of this problem. If you have encountered such issue, what was your solution?

System: High Sierra