It would help to understand what you mean by "not working as expected".
Is it not firing at all, ever?  Inconsistently?

If I had to take a guess based on what's shown, I'd bet its got something to do with your trigger mechanism.

This Send When option makes it so the notification must be called from a flow.  So *IF* your problem is that the notification isn't firing, your problem is in the Flow you expect it to fire from.