Trouble doing password co-op in Bloodborne with specific symptoms

I've been trying to do password co-op in Bloodborne with a friend and we're not connecting to each other. The weird thing is it has worked in the past and neither of us can figure out what the difference is this time. Seemingly nothing new has happened or changed.

He rings the beckoning bell, and I ring my small resonant bell. He tells me via text that in his game, fog walls appear as they do when you summon someone and parts of the world get blocked off to keep you in a specific level. But I never show up and in my game I am never summoned away, I never find his beckoning bell.

In addition, I will find that the game will eventually tell me my connection to the network is lost and I get kicked to the main menu. This doesn't happen to me normally, but for some reason trying to do co op like this it will happen within a few minutes.

Any ideas what the problem could be?

I know this is a super late response, but it sounds like it's a network issue, rather than anything to do with the game. Check your internet connection, or maybe your firewall.

If it's an internet connection issue, I would suggest simply re-staring your modem. For the most part, that should be all you need to do to fix any internet issues, if not, you may need to contact your ISP.

If it's not an internet connection issue, it may be your firewall. For the most part, the ports required should already be open, however you may need to open them yourself. This reddit post has a list of the ports that Bloodborne uses, including for online play.