If enough people complain about Acr recordings not working anymore. Samsung will have to take notice. I use call recordings for work. It's a handy tool to have on my phone.
Android 9 has removed the necessary access to phone call audio which all third-party call recorders use to function. I've had the same problem with Total Recall - it can no longer 'hear' the other side of the call, only my mic.
If you have a handset from certain regions, the Samsung system (root-access) call recorder feature is available. However for those of us with UK and EU handsets it's not available due to legal/privacy issues.
You could try rooting your handset, but then obviously you open yourself up to other issues.
This is not a Samsung issue, it's an Android issue. Welcome to Pie. 😞