I think somehow your screenshot location got changed to revert it back to the desktop typing defaults write com.apple.screencapture location Desktop

I think somehow your screenshot location got changed to revert it back to the desktop typing defaults write com.apple.screencapture location Desktop

There’s also discussion on this issue that could be related to finder slow to refresh or alternate locations for screenshots.

• Capturing screenshots on macOS Sierra is very slow
• Is there a way to refresh a Finder file listing?

The common thread is a third party sync or backup program like Google photos, box sync, Dropbox, etc...