Hey Sy4py,
I found some similar reports of this specific error in the past; it has often been caused by active options or configurations on the modem/router that need to be disabled or changed to avoid interfering with the connection to the game servers.
We don't have direct visibility into your configuration and active options to figure out exactly what it could be, though.
You might need to check with the ISP directly if you can't identify which option needs to be disabled in your case.
I appreciate you trying a few steps already, like switching to the Google DNS. Please also try the Open DNS, as suggested in this guide to troubleshoot your connection.
I would also recommend that you close all overlays and other background applications on the PC using this guide; sometimes another program on the PC is causing the problem.
Let us know how it goes.