Dead Space 3 coop broken in EA Desktop?

I had a similar issue, however I've managed to fix it. Idk if it will help you since I've seen lots of unsolved tickets about the DS3 co-op, but imo it's worth trying!

first of all - make sure that you are the friends with the person you are trying to play with (BOTH in the Xbox app and the EA Desktop).

Secondly - if you are getting these notifications (attachment 1.png and 2.png), you have to change the NAT settings. Go to the video below and follow the steps:

https://youtu.be/8wFn2Mxct4s

that's the second step (If nothing will help you can try this step aswell...), the third is adding some things as an exception to your firewall. 

Open your firewall
Go to advanced settings
Click Inbound Rules and then - add the New Rule, select Program, enter the path of your DS3 location and then click the deadspace3.exe
Allow the connection
Check everything (domain, private, public)
And name it however you want (in my case it was Dead Space 3 ANY bcuz you allow the game to use any internet protocol it wants, so you dont chose between the udp or tcp)

Make another rule, but this time select the Core folder in your DS3 directory and then click the ActivationUI.exe

Now go to your Control Panel, click Network and Internet, go to the Network and Sharing Center and click  Change adapter settings on the left. From there you should:
Disable and then Enable the internet connection. The name of connection will depend on what kind of the connection you are currently using, but in my case it was called Ethernet (basically the wired internet name), anyway that's the thing that helped me. Also, just in case, you can reboot your internet connection and restart the PC, but I don't think that's necessary.

Btw you can't send an invitation through the EA Desktop since the app doesn't support the invitation feature in the Dead Space 3 (which is really laughable). You have to make the public lobby and wait (for the person you are waiting for) to join, this person should seek for your lobby in the browse friend's games menu.

I hope this will help some of y'all. Imo it's worth trying, the game in the co-op is amazing, so the effort pays off!

EDIT: One more thing... I couldn't play today and i've spent lil more than an hour re-doing all the steps, and I've figured out that this game doesn't really like the Riot Vanguard, so if you'd like to play the DS3 co-op - you probably have to uninstall the valorant and riot vanguard in order to do so. Uninstall may be crucial, bcuz exiting vanguard didn't fix the issue in my case.