Matplotlib has a problem finding a backend after I use pyinstaller

I'm trying to make an .exe file from .py and I'm having an issue with matplotlib library. When I run my script in VS Code plt.show() works just fine. But when I use pyinstaller to make an .exe and run the .exe file, it gives me a following warning: "UserWarning: Matplotlib is currently using agg, which is a non-GUI backend, so cannot show the figure." Importing TkAgg directly with "import matplotlib.backends.backend_tkagg" doesn't solve the problem either. Is it possible to fix that?