unity – Additive Scene Loading Buttons not Becoming ‘Active’

I’m quite new to Unity but I’m making a game, and have created a simple Pause menu, when a key is pressed (escape), I just load a Pause scene, additively, and set that Pause scene to the active scene, however, only the buttons on the previous ‘game’ scene are interactive.
The mouseEnter, exit etc aren’t triggering on the pause menu buttons, despite the pause menu being overlayed on top of the ‘game’ scene; the Pause scene being the active one and the ‘game’ scene buttons are still the interactive ones (i.e. register clicks, mouse overs etc).

Obviously when I open the pause menu, I want the pause menu buttons to be the interactive ones (registering clicks, mouse over etc), not the previous ‘game’ scene buttons.

The pause menu scene interacts perfectly when loaded additively with a scene that had no buttons.

Many thanks.