Qt platform plugin issue -- What is this? Is it self-fixable by the common person?

Hi Meghan,

We'd like to verify a few things in order for us to assist you effectively. Kindly confirm the following:

• Were there any recent changes made to your computer prior to the issue? (Windows update, software or hardware installation, etc.)
• Have you tried the system restore?

This issue may happen due to system file corruption. We suggest running the System file checker. System File checker (SFC) scan is done to check if there are any corrupted system files that could be causing this issue. Kindly follow the steps below: 

1. Press Windows key**+ X**
2. Select Command prompt (Admin) to bring up elevated Command prompt.
3. In Command prompt, type sfc /scannow and press enter. (Take note of the space before the "/" )
4. Restart the computer.

Ref: Using System File Checker in Windows 10

If no corrupted system files were found, we suggest the following steps to deploy the DISM command lines: 

1. Press Windows key + X.
2. Click command prompt (Run as administrator).
3. In the Administrator: Command Prompt window, type the following commands. Press Enter key after each command: DISM.exe /Online /Cleanup-image /Scanhealth DISM.exe /Online /Cleanup-image /Restorehealth Important: When you run this command, DISM uses Windows Update to provide the files that are required to fix corruptions.
4. To close the Administrator: Command prompt window, type Exit, and then press Enter.  Click here for more information about running the DISM Tool.

Let us know if you need further assistance.

My experience wasn't exactly like yours, Meghan, but it may give you a start. I am working in Python in the PyCharm IDE. By default PyCharm 2018.1 gives you a project with a virtual environment (q.v.). The setup didn't copy the missing file to the venv; I solved it by switching to the global interpreter: File/Settings/Project:<name>/Project Interpreter. In the drop-down selection at the top, select the interpreter that is not in the venv. This removes much of the protection of the virtual environment, but that doesn't matter to a patzer like me. Hope this helps somewhat.

Joanna_777.  I did try a system restore, but the problem remains unchanged.  Thank you for the suggestion.  When I try to do the scan, it says that "elevated permissions are required."  I tried to go into my User Account Controls to see if I could fix that (based on advice from online), but I could not figure it out:

Do you have any recommendations for how to solve that problem?

Then if I do have a corrupted file, will I need to reinstall Windows somehow?

Also, when I tried to open the command prompt using the windows key + x, the only option to do something as an admin was Windows Powershell.  This seems to be different than command prompt, though?

Try typing in Command Prompt in the Start search box (Cortana).

Then right-click on Command Promptand select Run as administrator.

Concerning your original issue with QT, try booting in to Safe Mode and run your QT application. If everything works without the error code:

This application failed to start because it could not find or load the Qt platform plugin "windows" in "".  Reinstalling the application may fix this problem.

Then, we suggest contacting the developer of the problematic application and verify with them if the version you have will work with your version of Windows 10.

To confirm your exact version of Windows 10, just press Windows key + R > type in winver > Enter.

A window will appear like the one below.

Let us know how it turned out.

Joanna_777.  I did try a system restore, but the problem remains unchanged.  Thank you for the suggestion.  When I try to do the scan, it says that "elevated permissions are required."  I tried to go into my User Account Controls to see if I could fix that (based on advice from online), but I could not figure it out:

Do you have any recommendations for how to solve that problem?

Then if I do have a corrupted file, will I need to reinstall Windows somehow?