Recover hidden pictures from my system
From the Google play page of the app-


  Q - I uninstalled this app and again installed. Can I get my locked
  pictures back? A - You need to unlock pictures before uninstall. Files
  are not available in new install.


Unless you can get the phone working to access the app again you won't be able to decrypt the files. Decryption won't be possible on your computer too.