Thanks so much for your replies, Donald. I am using CorelDRAW 2021. I have a brand new MacBook Air that I bought about 2 weeks ago. It's got the new M1 chip, and apparently CorelDRAW 2021 was designed with it in mind. It's only got 8GB of RAM, but I've been assured that with the new chips, that is plenty for what I want to be able to do. I checked and I do not have the "enable background tasks" button checked. It's already off. I will ask about being able to upload a copy of the template, and will do so if the person I got it from is ok with it.
Thanks for the link to the video. It has a lot of good starting information, but unless I missed something somewhere, it doesn't talk about installation procedures.
For what it's worth, I am able to open other graphics files created from the templates in question. And then I can just edit those for what I need, by erasing what's already been drawn and starting over. But that's not ideal... (But it's a decent workaround for now.)