PyQt5 module not found, already compiled after installing (Mint)

Question

I've the problem, that programs didn't run since PyQt5 is missing:

    from PyQt5.QtCore import (
ModuleNotFoundError: No module named 'PyQt5'

I've already installed PyQt5:

Reading package lists... Done
Building dependency tree       
Reading state information... Done
python3-pyqt5 is already the newest version (5.14.1+dfsg-3build1).
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.

and compiled with

./configure
make
sudo make install

but it didn't help.

Do you have any help for me? My OS is Linux Mint.