F-Secure Deep Guard blocks PES 2018 online play
I had a problem for weeks as Pro Evolution Soccer 2018 suddenly stopped working online and displayed only error messages. I tried to solve it with Konami support work few weeks but we got nowhere. But now I just saw the solution posted on Steam PES 2018 discussion forum: the solution is to include PES2018.exe into F-Secure Deep Guard's excluded list. Once I did that the online gaming started to work again.
I suggest F-Secure checks out why PES2018.exe is blocked as it seems to cause problems to online gamers.
Here is the discussion forum on Steam on this topic: