i have this same issue. After playing for a day offline it gives me the activation error. I have found one way around this. When you get the activation message, close everything back out and shut off the blocker. Then open up either RPH or GTA and its going to ask you to log in to your Social club(make sure remember me and auto sign in is ticked). After you do it will go through its loading screen and then start the download for the update. Once it starts to download the update immediately close the window. Activate the blocker again and go back to RPH and it should let you play offline again. Has taken 2 tries before but it seems to be the best way i found around it.