The boop-boop sound indicates that the screenshot HAS been taken. The question is really where was the image saved?
The default OS settings saves screenshots on the desktop, so that's the first place to look.
IF you have your Finder configured to use Stacks (View -> Use Stacks) then screenshots may be combined into a screenshot folder on your desktop, so that would be the next place to look.
That is also assuming that Command-Shift-3/4 is set to save to a file and not to the clipboard. You can test the file vs. clipboard setting by taking a screenshot then going to Preview -> File -> New from Clipboard and seeing if your screenshot is on the clipboard.
It may be worth using System Settings -> Keyboard -> Keyboard Shortcuts -> Screenshots -> Restore Defaults to restore the default settings.
Failing all that, use Command-Shift-5 to bring up the screen capture control pane where you can use the Options to define where the screenshot should be saved.