There are many reasons why the Copy Paste command does not work on a Windows computer, such as your computer is attacked by a virus, the clipboard does not work, and therefore the copy command (Ctrl + C) and the paste command (Ctrl + V) do not work. So how to fix this error, please refer to the article below of WebTech360.
1. Fix Copy Paste command not working on Windows or on Office applications
Step 1: Scan your computer for viruses and malware
Note: Before proceeding with the next steps, make sure your computer is 100% free of any malicious software such as rootkits, malware, or viruses.
Step 2: Check the Copy and Paste shortcuts on available applications
To check the Copy/Paste shortcut key on Word, follow the steps below:
1. From the Word main menu, click Options.

2. Next, select Customize Ribbon in the left pane.

3. Click the Customize button next to "Keyboard shortcuts".
Under Customize Keyboard , select:
- Categories section => Home Tab.
- Commands => EditCopy.

Now under Current keys you will see 2 default shortcuts:
If you don't see the above 2 shortcut keys, click "Press new shortcut key" , then select the missing shortcut key and press Enter.
Perform the same steps on the EditCut and EditPaste commands. On the EditCut command, you will see 2 default shortcut keys:
On the EditPaste command you will see 2 default shortcuts:
4. Once done, check if the error persists. If the error persists, follow the steps below.
Step 3: Run Word (or Excel) without Plugins
Sometimes in some cases, adding plugins can cause serious errors in Word application. So to make sure that no plugins are causing errors in Word, you can run Word without any plugins. To do this:
1. Close Word.
2. Press the Windows + R key combination to open the Run command window. Then on the Run command window, enter the following command:
winword /safe

Note:
To run Excel in Safe Mode (without plugins), enter the command:
excel /safe
Now Microsoft Word application will open in Safe Mode and without loading any plugins.
4. From the Word main menu (File), find and click Options .
5. Next, select Add-ins in the left pane.

6. On the Manage Menu in the right pane, select COM Add-ins and then click Go....

7. Uncheck all the options to disable plugins and click OK.

8. Close and reopen Word in normal mode.
9. Check if the Copy-Cut-Paste command is working.
10. If the above commands work, the next step you need to do is go to Add-ins again and enable each plugin one by one to find out which plugin is causing the error.
Step 4: Uninstall Windows Update KB3057839
In some cases, Windows Security Update can be the cause of errors on the system. Update KB3057839 is reported to be one of the causes of errors with Copy-Paste commands.
1. Press the Windows + R key combination to open the Run command window.
2. On the Run command window, type the command below and press Enter to open the Windows Update window:
wuapp.exe

3. On the Windows Update window, find and click the Installed Updates link in the left pane.

4. Select KB3057839 Update and click Uninstall.

5. After uninstalling, check to see if the Copy/Paste command works. If it does, you should prevent future installations of KB3057839. To do this:
- On the Windows Update window, click Check for Updates.

- Select the Important Updates link.

- Right click on Update KB3057839 and select Hide update.

- Finally click OK.
Step 5: Disable security software
In some cases, security applications such as Webroot SecureAnywhere can be the cause of the Copy/Paste command not working error. To fix the error, you should temporarily disable the application.
To do this:
1. Double-click the Webroot shortcut icon on your Desktop.
2. Click on the Identity & Privacy tab .
3. Next, click Identity Shield in the left pane, then click View/Edit Protected Applications .

4. On the Protected Applications window, set the application to DENY .

2. Some other solutions
1. Uninstall any recent versions of IE.
2. If you have Skype Call to Click installed, you should uninstall the application in the Programs and Features section of the Control Panel window. In addition, you should completely uninstall the Skype application, then reinstall the latest version.
3. Use the System File Checker (SFC) tool to repair corrupted Windows files and services. To do this:
- Go to Start => All programs => Accessories => Command prompt , then right-click on Command Prompt and select Run as administrator.
- On the Command Prompt window, type the command below and press Enter:
SFC /SCANNOW
- Wait for the SFC tool to check and repair corrupted system files and services.
- Once the process is complete, restart your computer and check if the Copy/Paste command is working.
4. If you use a remote connection to connect to another computer, and the Copy/Paste command does not work after connecting, then you must kill and re-run the process "Rdpclip.exe". on the remote computer's clipboard. To do this:
- Right-click on the Taskbar and select Task Manager.
- On the Task Manager window, click the Processes tab .
- Select rdpclip.exe.
- Click End Process .
- Click the Application tab.
- Click New Process.
- Import rdpclip.
- Finally click OK.
5. Repair Office installation.
6. Check other keys.
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