Command r not working on Mac air 2015

The link provided next to this reply box, (upper left) offers a few ideas in connection

with Question Mark issue. There are two actual answers there; second one is better.

Learn what to do if your Mac starts up to a question mark.

https://support.apple.com/kb/HT204323

You may also choose to use macOS Recovery, or reinstall the system; etc.

Command r only works on powerup as soon as the screen lights.