What keys to hold down to boot in safe mode?

According to: How to use safe mode on your Mac - Apple Support

"How to use safe mode

1. Turn on or restart your Mac, then immediately press and hold the Shift key as your Mac starts up.
2. Release the key when you see the login window. ”Safe Boot” should appear in the upper-right corner.
3. Log in to your Mac. "

Press and hold the Shift key as your Mac starts up.

Use Safe Boot mode to isolate issues with your Mac:

https://support.apple.com/en-us/HT201262

According to the previously referenced article:

"If you still need help, please contact Apple Support."

I have done that several times and it won't work.