I am having exactly the same problem with Toast 18 / on a new install of Catalina, but with a brand new version (downloaded from the Roxio store). I purchased the Toast 18 Pro version Sunday night gone, but the only thing to open so far is the crash report. I have been using Toast for many years so I have tried all of the tricks e.g. delete prefs etc but this app is a dead duck. I raised a ticket with roxio and included the apple crash report on Sunday night, I am still waiting for a reply, it is only Tuesday so I will give it until tomorrow afternoon then I will call them.
I have spent over £100 (including a disk copy) on this app so far and I am not very happy as my Blu-ray writer is turning up tomorrow and I can't use it.