Hello,
There is a new version of Switch which works with Catalina OS, you can download and install it from the link below:
https://www.nch.com.au/components/switchmaci.zip
Do keep in mind that your license needs to be compatible with this version of the program to be able to register using your registration details.
You can try reaching out to NCH Tech support if you need more information, you can create a support ticket for them through the link below:
- https://www.nch.com.au/support/index.html 
Good luck!