Error: “To open this spreadsheet, you’ll need the latest version of Numbers”

Running Catalina 10.15.7 on a mid-2012 MBP. Starting in the fall of 2021, when trying to open a certain Numbers file on my Mac, I get a “To open this spreadsheet, you’ll need the latest version of Numbers” error box that never appeared before. Other threads mention that one culprit for this is opening the file in iCloud.com in the latest version of Numbers. However, there are other Numbers files I’ve opened recently via iCloud.com that still open just fine on my Mac. It only seems to be this one particular file (which happens to be password-protected), the contents of which haven’t changed much since the fall. It is not a shared doc and is not in a shared folder. Any suggestions on a workaround?