Thanks for the suggestions. There is only one copy of Inkscape on my computer. I deleted everything Xquartz or X11 and reinstalled Xquartz (just to make sure) then rebooted the computer. When I opened up Inkscape from the Applications folder it asked “Where is X11” and I pointed it to Xquartz. The same error message showed up (opening Inkscape directly and by opening a file).
I did the “Show in Finder” and the applications in use are Inkscape and Xquartz.