Probably. This is a straightforward feature in Axure. In the editor, select a widget, click “New Interaction” in the INTERACTIONS panel, then click “:mouseover” under “STYLE EFFECTS” at the bottom of the list. Looks like you’ve done that. If it doesn’t work, what other interactions do you have for that widget, group, dynamic panel, etc? Check if there are any widgets in front of your rectangle which might be blocking it. In most browsers, you can Inspect the widget (right-click it in the browser and choose Inspect) --then, when you hover over it, the HTML should change to include “mouseover” in the "div class= " section. If not, something is blocking it.
Here is a quick demo of the :mouseover style to show how it should work for you.
mouseover effect.rp (48.7 KB)
If you still have issues or questions, I recommend uploading your file so forum users can look at it and apply fixes. (Look for the little up-arrow icon in the Reply window control menu, just to left of bullet-list icon.)