Note that Dying Light does not support LAN connections by default, while starting from around 93% (both in the Main Campaign and The Following), all the quests (including side quests) need to be completed in single-player only by design. Once you complete the main campaign to 100%, co-op will become unlocked again. 


In addition to that, Dying Light uses the same ports as your platform recommended ports. For more information, head over to:

It is also possible that your online experience is affected by your NAT type.

In general:
  • NAT 1 can be connected with NAT 1,
  • NAT 2 and NAT 3 NAT 2 can be connected with NAT 1 and NAT 2, but not NAT 3
  • NAT 3 can be connected with NAT 1, but not NAT 2 or NAT 3

For more information, consult the following articles on multiplayer solutions and testing your system connection on Xbox One and PS4 respectively, please:
http://support.xbox.com/en-US/xbox-one/networking/nat-error-solution

http://manuals.playstation.net/document/en/ps4/settings/nw_test.html


If your platform is Steam, you may also have the so-called Moderate NAT type, while Dying Light, along with a number of other multiplayer games, heavily relies on NAT.


Change your NAT to Open, please. Unfortunately, we have no guides on NAT configuration for the PC platform to officially share.


Additionally, if you have your Internet router set to IPV6, try changing it to IPV4.


Lastly, note that it may be difficult for your console to connect to a Dying Light co-op session twice from the same source (e.g. in the same house/within the same network type). Only one console can connect from a network at a time. However, you can search the Internet for articles on how to set up a DMZ for your console, which might solve the issue at your end. 


If the above advice has not fixed the issue at your end, send us a report about it including answers to the following questions, please:


  1. How far are you and the other co-op players into the game's story-line - does the game indicate about 93% of progression for any of you?
  2. Are you trying to connect to each other on the same Network / in the same house?
  3. Do you Game-Share or Family-Share Dying Light with other players?
  4. Which gaming platform is your issue connected with - Steam PC, PS4 or Xbox One (X, S or the regular Xbox One console)?