I don't know SP or how its shortcuts work, but did you check if you already have those shortcuts assigned in plasma's global shortcuts? The easiest way is to assign them to any plasma global shortcut and see if it tells you there's a conflict.
If that's not it, can you trigger those SP actions with an external command? Then you could do it through plasma global shortcuts.
I searched and found the project. If you're having the same issue described here, it's been known for a few weeks and