Unable to "Copy" text from PDF, but still able to "Copy With Formatting"

Hi all,

Over the past month or so, I lost the ability to copy text from PDF files (Ctrl + C). Right clicking and choosing "Copy" also does not work. If I go into Excel and "Paste" (Crtl + V), nothing happens. 

I can, however, right click and choose "Copy With Formatting," which is confusing. I can paste it into Excel.

It makes me think the issue is not PDF protection or anything. I checked "Security (Enhanced)" in Preferences and confirm that "Protected Mode" is disabled.

Can somebody please advise?  

Thank you.