I can't select dropdown item

I have a QTableWidget with dropdown inside each cell as shown in the attached image. When I enable VoiceOver, I can navigate to the left most dropdown and VoiceOver will read each element as I use the up/down arrow key. However, I can't activate the item using the spacebar or enter key. VoiceOver reads the dropdown item as text element. 

Another problem is that I can navigate to the cells on the right but I can't focus on the dropdown inside the cell and interact with it.