Why does the Can't write image data to path error occur?

Question

Laravel

I usually store uploaded photos with $file->store('public/portfolio/'.Auth::user()->id), this way works.
But to create thumbnails I started using intervention image, $file->save(public_path($pathT)), but it doesn't work.
Obviously there are rights, since the store works. Tried without public_path(), tried relative and absolute paths. In Image.php: 'driver' => 'gd'.
Laravel 5 version
Thank you!