I have LR catalogs dating back to 2010. Each time LR updates, I am unable to access older catalogs. What do I do?

You’re probably worried that upgrading an old catalog that has an old version of Lightroom will apply changes.to your photos. That’s not the case, unless you actually make edits. So there’s no problem to have them in an up to date catalog.

When it says to update, do you click on the button that tells LrC to do the update? You have to do that with certain updates to the LrC software.

Then you say: “Now, when I go to open catalogs on older hard drives, I can’t!” Why can’t you? What steps do you follow? Describe the problem. Tell us what the error message is.

Sure you can open an older catalog in the latest version of Lightroom Classic. Lightroom will create an upgraded copy of that catalog and open that. That is what this message tells you, not that you need to upgrade Lightroom, because that has already happen.