If you are unable to open the Toonly software on your Mac due to a notarization error, kindly follow the steps found here: https://support.apple.com/en-us/HT202491
Running software that hasn’t been signed and notarized may expose your computer and personal information to malware that can harm your Mac or compromise your privacy. If you’re certain that an app you want to install is from a trustworthy source that hasn’t been tampered with, you can temporarily override your Mac's security settings to open it.
In Mac OS Catalina and Mac OS Mojave, when an app fails to install because it hasn’t been notarized or is from an unidentified developer, it will appear in System Preferences > Security & Privacy, under the General tab. Click Open Anyway to confirm your intent to open or install the app.