App Store error when try get macOS Catalina Installer

I'm follow this tutorial do downgrade my macOS: https://support.apple.com/en-us/HT211683. So to get installer I'm clicking on macOS Catalina 10.15 link and it brings me to open a App Store link, so ok, but when I enter on App Store from this link an error is triggered on my computer: "Cannot connect to App Store". Also, I tried search directly on App Store for: macOS Catalina, but nothing is found. So, how I can get the macOS Catalina to downgrade my problematic Big Sur?