File Access Issue Since Upgrading to OS X Capitan

I have a file access issue that has begun only after updating the OS to OS X El Capitan 10.11.6. I have an Excel 2016 workbook that has VBA code behind that processes (opens, read, copies) from other Excel books in a subfolder. The first time I access a new file from the code, I am prompted to “Grant Access.” In the past the “Grant Access” button was blue and I clicked it and away we went. Now the “Grant Access” button is gray, and when I click it, the code aborts trying to open the file, indicating that access was not granted. This happens whether the file is local or on a network share. What might be my issue? Thanks for any help! 🙂