In a multiplayer tips post for Bloodborne today, Producer Masaaki Yamagiwa revealed that From Software is working on a fix to address Rest mode issues with matchmaking:
Utilizing the new Suspend/Resume feature to put the PS4 into Rest mode without shutting down the game first causes players to be unable to complete matchmaking. Please be sure to restart the game in order to make sure you are able to connect online and matchmake for multiplayer.
This issue will be addressed in an upcoming patch.
It remains to be seen if this fix will be included in the update to improve load times, or if it will be given out separately.
How far are you in Bloodborne right now?
[Source: PS Blog]