UltraMixer 6 does not yet support macOS 10.15 (Catalina). Currently we recommend that you should not upgrade to macOS 10.15 Catalina. The current macOS update has major problems installing UltraMixer 6.
We are working to ensure that UltraMixer 6 is fully compatible with the new macOS update.
In the meantime, we recommend you stay with the latest macOS version until further notice.