Hi @Anthony Green ,
Please go to the Control Panel and try to repair Microsoft Visual Studio Tools for Applications 2019
UPDATE
Finally, Microsoft posted a fix:
"...There is a regression in VS 2019 16.9 that will cause script task/component not work properly when editing script. VSTA team has released a new version to work around this issue. Please download the latest version of VSTA 2019 here and manually install it to work around the issue..."
So the installation of the Microsoft Visual Studio Tools for Applications 16.0 will fix the issue.