What to do if it says that pyinstaller is not an internal command?

Question

Python

Downgraded pip to 18 installed payinstaller.
pyinstaller==4.1
Tried to compile to exe.
Issued

"pyinstaller" не является внутренней или внешней
командой, исполняемой программой или пакетным файлом.

I upgraded to a new version of pip, I don’t know why, I did the same thing again.

Answer 1

Add the path to pyinstaller to the PATH system variable.

Answer 2

python -m pip install auto-py-to-exe
auto_py_to_exe

This is the same pyinstaller but with a GUI

Answer 3

py -m pip install pyinstaller
it worked for me