Catalina compatibility

I have a MacBook Pro (Retina, 13-inch) Early 2013.

According to the official list, this machine is Catalina compatible.

However, I cannot access the Catalina update software via System Preferences, then Software Update.

My Macbook Pro is considered running the latest update (Mojave 10.14.6).

On the AppleStore I find OS Catalina and the system indicates that my MacBook is compatible.

But when I hit the GET button, the system responds with "Update not found" and "The requested version of MacOS is not available".

What exactly applies to my MacBook Pro ?

Thanks for helping out.