It must be the firewall that prevent the outbound traffic from your GTA V.
Unblock the outbound traffic on Windows firewall for GTA V exe file. Please refer to Windows guide on how to do that.
If that failed, the firewall is not set properly.
To test it, you can temporarily unblock all outbound traffic on Windows firewall.
I got an e-mail from another user with similar issue. He managed to solve that:
hello Bejo!
i just wanna say thank you for your help and support for the mod, it took me a little to understand but i finally found the outbound requests and gave gtaV permissions and TA-DA! its working perfectly!
I'm going to work so I don't have time to test this, but this is what Bejo sent me.