why won't it allow me to find the download for macos10.15.

Hi,

You can download Catalina from following site.

https://apps.apple.com/us/app/macos-catalina/id1466841314?mt=12

What are you doing to try to get it? Also, there is no information such as what computer you are using. In order to be able to successfully help you, the more information you can give the better. What things have you tried, what happens with the way that you are trying to do? If you are trying to download it using Software Update, then the problem may be that the computer does not support a version of OS higher than what it is already running. Without knowing what hardware you are using, then it is not possible for us to be able to determine what it is that could be causing the problem.