AppleScripts to create Calendar Events not working in Catalina

Solution 1:

OK, I've made some changes so that I can run the Script in Script Editor (by giving the variables plain text strings rather than extracting them from the email).

When I run the script I get the following error: error "Calendar got an error: Can’t get calendar "Invoices"." number -1728 from calendar "Invoices"

That gives me a clue I guess - although the Calendar that it should be adding the event to does exist in my Calendar app. Could it be something to do with the quotes around "Calendar" and "Invoices" in the following line of the script?

tell application "Calendar" to tell calendar "Invoices"