There are several potential workarounds to this issue. Please work through the following steps to see if they fix the problem:
🛠 Make sure you have enabled CROSSPLAY.
In your game options, select the Game tab and make sure that the Enable Crossplay box is checked for both players.
🛠 Make sure you are on the latest game build.
If an update was released recently, you will need to be on the latest build to play with the rest of the community.
🛠 Make sure your local or campus firewall is not blocking connections.
Make sure the game is whitelisted so it doesn’t get blocked in the matchmaking lobby.