I'm experiencing this same problem described by someone else here:
It says the discussion is closed, so I can't post in the reply. There is a link of the issue, but that page no longer exists either.
I'm using Quicken Classic Premier v 8.0.1 (build 800.56243.100), macOS 15.3.1
I also tried to manually create the Check in the account itself, and when it goes to create the Payee, I get the same error message.
Help please. Thx.