Sometimes when you backup your data using either the 'Air Transfer' feature or the 'Dropbox auto backup' feature, the backup doesn't happen properly resulting in a '22Byte' file. If this is the result of your latest backup (which you can verify in your computer's Downloads folder & Dropbox respectively) and you need to re-install the app then kindly perform a backup using the iTunes method instead - http://noteshelf-support.fluidtouch.biz/hc/en-us/articles/214368958-Via-iTunes
This is bug that got introduced with our last release due to some internal changes we had made.
We are working on this and will be issuing a fix for it in our next release. ETA TBD. Kindly bear with us shortly.