Error when running code that uses PyQt5 library?

Question

PyQt

For some time now, I've been facing an error like:

qt.qpa.plugin: Could not find the Qt platform plugin "windows" in "C:\Users\└yoshifshe\AppData\Local\Programs\Python\Python37\Lib\site-packages\PyQt5\Qt\plugins\platforms"
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.

There are many videos on YouTube with similar errors, but they did not help me. In the text of the error, the Python folder, for some reason, is 37, not 39. Other Python folders, I deleted just yesterday, and reinstalled Python itself. Copying the platforms folder from the PyQt5/Qt/plugins/ folder does nothing. Yes, and this folder, in principle, is not. I tried to create this folder myself, and transferred a copy to the Python folder itself, it did not work. I tried to transfer the platforms folder to the PyQt5 folder in the same way. Exactly the same - no result.
Python 3.9.0 64-bit.