Activity monitor

Hi

I'm no longer able to get the information about which programme affects my cpu load, memory or how much energy is used within the activity monitor.

If I click the (empty) bar that I could use to select a category before, it only sorts them by name.

I can close the programme or shut down my computer, both won't solve the problem. Neither did the last two updates.

Would anybody know why that is or could suggest a solution?

Many thanks