Summon issues

I am playing on PS5, but i’m playing the ps4 version of the game. My friend is playing on ps4. I summoned him for all of stormveil castle about a week ago, but since then we haven’t been able to connect. Is there any known issues for ps5 to ps4 connections? Are there any known fixes? We’ve played together on souls games for years without issue.

Thanks for any info