I don't have any files in my account but it says storage is full.

Hi there,

Welcome to Box Community!

Note: If you ever come across these data inaccuracies in your account, please know that the problem is entirely with the display of these totals. This has no effect on your underlying data. All of your files remain in place and have not decreased in size or been edited by unauthorized people.

Please keep in mind the following information about storage calculations: 

• Trash is excluded from your overall storage calculation.


• If you are collaborating with another user in a folder they own, the storage is calculated only as part of the owner's account and will not count toward your storage calculation.

Most of the time, aggregates will be updated within an hour or less. For larger changes or more complex folder structures, aggregates may take up to 24 hours to be correct.
 
For reference, you can visit this article. https://support.box.com/hc/en-us/articles/360043695334-Storage-Usage-Or-File-Count-In-My-Account-Is-Incorrect
 
Thanks for posting!

Best,
Ann