If the dialog asks "Do you wish to continue" simply press "Yes" to update your game storage.
However, if you receive an error message such as "DLC files are missing, make sure your game is up to date," please follow the instructions found here to verify your GTA V installation.
Also, double-check that your CitizenFX.ini file points to the correct GTA V installation. You can locate this file within your FiveM application data.