Excel macros that worked fine for years now err on the simplest commands

Tonefish 

If I may suggest, add more information about your problem.

Information such as the code itself. Digital environment such as Excel version, operating system, storage medium, excel file extension, etc.

This would help other users to make a more accurate solution suggestion.

Nonetheless, here are some possibilities/reasons:

There could be several reasons why your Excel macros are not working. It could be due to a recent update or change in your system settings. You can try some of these solutions:

• Recompile Macros
• Repair Microsoft Office or/and the file
• Install Latest Windows Updates on Your Computer
• Clean Boot or Different Startup Options
• Disable Add-ins
• Start Excel in Safe Mode
• Look for the Presence of Any Third-Party App that Can Hinder Excel from Running Macro
• Resolve Antivirus Software Issues

You can find more details on how to troubleshoot macros in Excel not working here.

I hope this helps!