Anybody else seeing this?

It happens periodically, and if I quit AM and trash /Users/artie/Library/Preferences/com.apple.ActivityMonitor.plist the window is fully populated when I relaunch...no restart necessary.

It's new in Catalina.

Just to check, I launched AM (which I rarely do) and everything was normal. I realize that this does not replicate your procedure, of course. Have you reported this to Apple?

It happens only once in maybe 10-20 launches...maybe a bit more often; you can't just launch and expect.

I should file a bug report, and I would already have done so if a restart were required, but dealing with it is less painful to me than going through Apple's bug report procedure. Maybe if it isn't fixed in 10.15.6.

FWIW, I launched AM and got the same thing you did and this is in MacOS 10.15.6. I am reporting it.

Thanks for relieving me of the legwork.

The Feedback assistant that comes with the beta releases makes it easier.

I'm all in for beta testing my apps, but I don't feel like I'm up to testing macOS despite the fact that I actually do identify bugs (when I"m paying attention).

In MacOS 10.15.6 beta the Activity Monitor display its is caused by the Name field being so wide that it pushes all the other columns off the screen to the right, and the right boundary of the name field cannot be dragged far enough to the left to make the data visible unless you are in Full Screen mode and even then not all the columns appear. Irritating! 😡

One good, sharp whack on the wrist with a ruler for you for failing to have noticed the horizontal scroll bar in my screenshot...and two of 'em for me for having noticed it once and corrected the situation by the obvious, but hardly intuitive, method of scrolling to the right and dragging the Process Name column back to its correct width...and totally forgotten about it.

So it seems as if nothing has changed in 10.15.6.

True I did fail to notice the scroll bar in your screenshot. I failed to notice it in my Activity Monitor window at first. But although I can scroll to the information I cannot get the process name and information on the screen at the same time, because the name field is too wide and cannot be dragged to the correct size! That is annoying and seriously compromises the app's functionality.

I was able to drag my name field to the correct size both times I noticed the scroll bar, although it was faaar from as easy as it should have been.

Update: It just happened again, and it took a BUNCH of doing - I ultimately switched from the Memory tab to the CPU tab - but I WAS able to get all of my columns on my screen at once...100% success rate...if you don't count how long it took to get the job done.

Yeah, it IS a giant PIA, particularly if you're looking for immediate info.

I got it to work this morning just like it is supposed to and to my knowledge, nothing has changed on my system in the interim, not even a reboot.

My problem is totally erratic...not at all consistent.

I can launch AM time after time after time without it happening, and then...out of the blue.

I just discovered that even though it looks as if nothing is happening when you try to drag the columns from right to left, in reality, if you drag long enough, the columns on the left will appear on your screen.