Every time I try to add a comment by selecting the the "Comment" toolbar and clicking the "T" to add text, and then clicking in an area I wish to insert text, I get the error "Can't Fetch cmaps" as soon as I begin to type. What could be causing this issue?
Is this an issue with a particular PDF file or with all the PDFs? Please try with a different PDF file and check. If the file is stored on a shared network/drive please download it to your computer locally and then try again.
What is the version of the Acrobat DC you are using? To check the version go to Help > About Acrobat and make sure you have the recent version 23.06.20320 installed. Go to Help > Check for updates and reboot the computer once.
You may also try to create a new test user profile with full admin rights in Win or enable the root account in MAC and try using the application there and check.