Screenshots not showing on desktop in Mac OS 26.2

Prior to upgrading to Mac OS 26.2, Command-shift-4 would cause a .pdf file to appear on desktop.  Now, Command-shift-4 does nothing; I can find no file created anywhere.  Now, after clicking on the SCREENSHOT App, and using its icons, I have tried several "save to” options.  

1.        “Save to desktop” does nothing – no file is created, nor shows up anywhere.

2.        “Save to Preview” causes the untitled picture to show up when I open Preview

3.        After creating a new Folder “Sav”, nothing shows up in Sav; and no file is created.

How can I go back to the simple step, prior to 26.2. ?