After taking a screenshot, an error occurs when I paste it into the app

Your capture is reaching the clipboard, because Word can paste it; the difference is what each destination accepts. Win + Shift + S places image data on the clipboard, not a normal image file. File Explorer therefore cannot paste it into a folder as a file. After the capture, open the Snipping Tool notification and press Ctrl+S, or use Save as, to create a PNG; then copy or drag that file into File Explorer. In a chat app, use its Attach or Upload command if direct Ctrl+V is unsupported or unreliable. To test the clipboard itself, capture again, open Snipping Tool, press Ctrl+C, and paste into Paint or Word. If that also fails intermittently, go to Settings > Apps > Installed apps > Snipping Tool > Advanced options, select Repair, and test again; use Reset only if Repair does not help. Also install pending Windows and Microsoft Store app updates.