too long, still 0% after one hour ?

The savegames are very large, so it takes some time to upload them. Also, check the folder where the savegames are stored, last time I looked on my box I had tens of savegames which amounted to hundreds of MBs in size. Try to move everything from there, except the most recent savegames you want to keep, to a temporary folder and retry the sync. If everything is fine you can delete the temp folder.

Keep in mind there is cloud limit too.