Hi ,
Welcome to the Support Portal. How can we help?

A site is empty or missing from the Documents app. How do I fix this?

It could happen that a site is missing from the Documents app. Or perhaps the site is visible, but no files are shown within a folder.

It is import to know how Workspace retrieves these sites. What happens when these sites are not even being indexed by the SharePoint Search? Or perhaps sites contain too many items? What does it mean when Faster Loading Experience is enabled? And what about permissions? And is there a difference between a Teams site or SharePoint site? These are all important questions to ask when troubleshooting this topic.

To give you a bit more background information, take a look at our article on troubleshooting SharePoint