If you havent already, to resolve many initital issues, please check you have the latest updates for your PC. Windows/Mac/Linux. Please also check your Graphics Drivers are upto date. If you have done this then the following may help you further.
Connection Issues – Unet
Start the game launcher via steam. Games>right mouse click on 7 Days select show launcher. Then select Disable Unet.
Connection Issues – EAC
Please note that any requirement to disable EAC on games may also affect 7 days. Please ensure this is enabled and running via your task manager.
EAC Needs to be active and enabled in your game or you will always have connection issues and this could bring the attention of your activity to Steam, EAC, Developers and the servers administrators.
Graphics Card Settings
In order to achieve maximum performance and the best graphical result please ensure that your GFX card has all 3D settings that are applicable to application controlled.