keyboard.send('enter') doesn't work on 'Save As' pop-up window

Question

I have a simple Python script that just clicks on already opened Browser window, preses 'Ctrl+s' and saves the page.

It works until 'Save As' pop-up window appears, so in below code ctrl+s works but the last doesn't

import keyboard, mouse

mouse.move(100,200)
mouse.click()
keyboard.send('ctrl+s')
keyboard.send('enter')

Any idea why?