Unable to use Completions. How do Completions/shortcuts work?

[AIMLDevRnD]

I am trying to launch completions shortcut by following the shortcut keys in the completions app as below:

I tried using the completions app in different apps, with app in background, but nothing works. Not even a pop up showing the completions. I am able to open the spotlight search sort of shortcut though. Would highly appreciate any insights here? Am I missing something? Are the shortcut key combination for completions inaccurate or is the functionality broken?