having this issue myself on PS5.
My process left the rat pact open -- I didn't make one, but I didn't rule it out. I encountered them early in the Gauntlet of Shar, and killed 3 out of the 4 that try to ambush you with some alchemists fire. I just left after speaking with the lone survivor so I didn't make it worse, but I left the relationship relatively open.
But before I got to Yurgir and even knew I needed to kill the Rat Man Dark Justiciar, I ran into the broken effigy at the feet of the Shar statue.
I had to kill a rat at the top of the cragged rock because it was blocking my path to get to the bottom, and when I went down the craggy rock to get to the skull-salted base, my avatar PC looked around like something shifty was happening, but ultimately no cut-scene triggered. No flood of sleep-rats, nothing. I didn't know about the Yurgir contract yet though, so I figured I just wasn't supposed to know what this area does yet, and moved on -- like maybe it's a story point I just haven't gotten to yet, so I moved on and found Yurgir.
He kept tanking my party (partly because I skipped the grymforge because I couldn't figure out how to trigger the magma and Grym, and thus have no adamantine armor or weapons) so I looked online for some tips and found the rat guy plotline.
I can't get past Yurgir in a fight, so I need to get past him in another way, and that other way isn't triggering.

I don't want to scale down my difficulty, so now i'm just stuck waiting for an update.