Activity Monitor columns are gone

Thank you for the suggestion. I finally had time to return to this problem today and try booting into Safe Mode as you suggest.

However the problem still persists. While operating in safe mode, my activity monitor does not show any of the columns. And when I go into my Library folder (while still in safe mode), I do not find the preferences file that (I think) should be there for the activity monitor application.

If I am interpreting this correctly, that should mean that the problem is not being caused by some interference that a particular third-party app may be causing when loading during computer start.

Some additional info regarding my computer and how I use it.

I did recently upgrade the RAM in my iMac (Retina 5K, 27-inch, Late 2014) from the standard 8 GB to 32 GB, using RAM that I purchased from Best Buy and installed myself (4 x 8 GB modules). My system info does show that the memory is correctly installed and being recognized (About This Mac states that I have 32 GB now).

My use of this computer is very straightforward; I don't use many apps beyond the standard iMac package.

What I do use frequently are Microsoft Office applications (primarily Word for Mac, and Excel for Mac), and other browsers in addition to Safari (Chrome, Opera, Firefox).

The one software change that I have made to my computer recently, other than the upgrade to OS 10.15.4, was to install Parallels for Mac, so that I could have Windows capability. I also installed VMware Horizon Client, to give me the capability to remote access my work computer while working at home.

I don't know exactly when the problem with Activity Monitor began, because I don't use it every day. I do know that after beginning to use Parallels and VMware, I was curious to see how much RAM was being used by those programs, so I opened Activity Monitor. That was when I first noticed this issue.

Thank you - it did locate the file, I deleted it, problem now fixed!

It is not at all clear to me why I could not locate the file by using 'search' when in a finder window or using Spotlight Search, but both of those methods did not result in my finding the file. My mistake was not understanding that there are more than one preference folders and this file was buried within the Users hierarchy which is not the preference folder I was going to when manually drilling down using one of the finder windows.

Thanks very much for your help. It is a reminder to me of the file system hierarchy in the Mac that I don't often think about, since I don't need to to dealing with system settings or other things like this very often at all.

I much appreciate your assistance.