Thanks for responding Doug. The problem is not with a single xlsm file, but with every xlsm I have. Whichever one I choose to open, it gives me the same or similar error as I mentioned above. Macros will not work. All of these xlsm files were created in
versions of Excel earlier than Excel 2016. This issue appears to be with the upgrade to Office 2016 I did a week ago. I've never seen these errors before in Excel 2013 or prior versions.
Furthermore, I just did a quick test: I created a new xlsm file (the first xlsm file I've created in Excel 2016). Right away I see that on the Developer ribbon the Visual Basic and Macros buttons are grayed out. Changing the Macro Settings to "Enable all
Macros" doesn't help.
The next thing I tried was to create a Word docm file and marco. Starting with a new docm file, I ran the macro recorder with the following error:

The heading of this error box says that when the software was installed, I chose not to install support for macros or controls. I'm pretty sure I wasn't asked whether or not I wanted macro support when I upgraded to Office 2016. Again, on the Developer ribbon
the Visual Basic and Macros buttons are grayed out. I also see that in Outlook, on the Developer ribbon, the Visual Basic button is grayed out. The common thread seems to be a faulty upgrade? Should I do a complete re-install of everything?
Thanks