Here is the image file.
Even though you say you are running Isadora v3, this error. would indicate otherwise.
Instead, it seems that you are attempting to run Isadora v2 on Catalina, which is not possible because it is a Isadora v2 is 32 bit app and Catalina will only run 64 bit apps. (macOS Mojave and older ran both 32 and 64 bit apps.)
This error is described on this page from Apple where it says "When you attempt to open a 32-bit app, you will see an alert that the app needs to be updated to work with this version of macOS, or that the app is not optimized for your Mac and needs to be updated." It shows the same dialog you attached above.
You must upgrade to Isadora v3 if you want to run Isadora under Catalina. You can download the latest version of Isadora 3 from our "get it" page.