I was having trouble for about a week. I tried everything from deleting friends to deleting and re-installing the game, and almost everything mentioned with no success. I also tried to delete the save file alone and that didn't work. I was attempting to troubleshoot and got it to work by doing the following (I have no idea which of these steps actually worked, but I'll list them all just in case they can help someone):
!. Delete game save file on your console.
2. Make sure you are no set as "show offline" (not likely the issue, but just in case), make sure it shows you are actually online on the console.
3. Go to system settings and date/time (for the PS4 version) and make sure the box is checked that says set date/time automatically, and then click set automatically via internet.
4. Run a network connection test in the settings.
I'm not sure why any of this worked, but I've been checking every day all week and these steps were the only thing I could do to get it to work. I think the date and time on the console was the problem for me, even though it was set correctly. Regardless, I have it running now and it is working fine, despite it not even working an hour ago when I last tried several times.
EDIT: Can confirm, the game wouldn't allow me to connect due to my date/time settings. Went into settings, changed the date and time info so that it was wrong and couldn't connect. Changed it back and got an instant connection.
