Seems like riot won't answer to any thread about this error so I'll make another one. Maybe one day the forum will be full of it and they will finally realise that this happens to people since july !?!?!?!

So here it is ! After champion selection , no loading screen no nothing just plain black. Error pops off after 30 seconds saying your firewall might be (i like the might) blocking your connection to the server. Makes this error 1-2 game per day. randomly. No particular reason just troll servers.

YES my firewalls are off.
NO I don't have an antivirus on blocking connection.
YES my router's port are open.

Just to make sure again , YES my firewalls are off.

Thanks in advance for no answer.

Worst regards.

I finally found how to resolve it, uninstall and never install it again.

GG wp

I had this problem and I had to reinstall, it made me get a leave twice though