If you've encountered the GTA Online PC connection issue, then you've probably tried to join a session but been presented with a message saying "GTA Online will be available once you have completed the Prologue" or another error response. This problem has appeared as a result of the recent security update to fix the exploit that let griefers corrupt player accounts, with the (perhaps unintended) consequence that measures put in place by players to protect themselves from the hackers are now working against them.
It's not clear if this will be a permanent issue to work around in GTA Online, or if it will be resolved with a further update, but naturally if you're on PC then you want to play now. Helpfully, there is a solution available that players have been using to join the game, so here are the details for how to fix the GTA Online PC connection issue and return to Los Santos.
How to connect to GTA Online on PC
To fix the GTA Online PC connection issue, you need to turn off any additional firewall or port blocking rules you have in place for your machine. Ironically, players were originally using these measures to protect themselves from hackers, but following the security update Rockstar are now preventing players with port blocking active from logging in the GTA Online.
Once you've established a connection to the servers, you should be able to turn your firewall and port blocking back on while still playing, and even join new sessions, though some players have reported potential issues with entering missions and other activities. Now the security patch has been deployed it should be safe to play without additional protection, but that's a matter of personal choice and whether you have confidence in the fix.
