make a new document
make a drawing
close and save it
realize you need to add something
so open the document
Fusion will tell you this:

I waited few minutes till I had enough went offline and then simply edited the file, went back online and let it sync.
A file like some lines should take few seconds to upload but not make a designer wait minutes.
So maybe while syncing simply stop it when you want to re-open the file.
and let it sync again once you close it.