It may be because you haven't linked your PS3 to Uplay, in the beta, you can only link your console from the pop-up Uplay screens that appear when you launch the beta – make sure to complete this process if you want to access the GRN.
Which features of the GunSmith Gallery will be available during the beta ? How does it compare with the features available near GRFS final launch on May 22nd ?
Accessible all the time
GunSmith Free mode – try out weapons and their entire attachments sets to make your own unique weapon. Weapons cannot be synced to your console. Note : new weapons will be published regularlyin GunSmith free mode from beta till launch
GunSmith Gallery (coming soon) – post your unique weapons for everyone to see, or find a weapon you like created by others
Community news in Ghost Feed – get updates from the GRFS community from your main menu
Heatmaps – check them
Accessible only during beta (April 19th till end of April)
GunSmith Sync mode – customize your weapon anywhere, and sync it to your console