Original issue:
Can’t start coop games.
The issue happened after the 4.10.3.76114 update.
The Ready button isn’t available.
The game just keeps on the “Initializing game state”.
Solution:
Delete all Starcraft firewall rules.
Start starcraft again.
This will get a popup saying to allow. Give that permission.
(This will not be enough)
Look at the firewall rules, a couple of inbound lines will still say that they are blocked. Allow them.