How we can click on buttons which is inside in Process Flow control in SAPUI5?

I have added two buttons(Approve, Reject) in Process Flow node. But I am not able to click on that buttons.

Can anyone help on this, How we can click on that buttons?

sap.suite.ui.commons.ProcessFlow

ProcessFlow Control

Code:

<ProcessFlow id="processflow1" scrollable="false" nodePress="onNodePress" foldedCorners="true" nodes="{/nodes}" lanes="{/lanes}">
			<nodes>
				<ProcessFlowNode id="processflownode1" laneId="{lane}" nodeId="{id}" title="{title}" titleAbbreviation="{titleAbbreviation}"
					children="{children}" state="Neutral" stateText="{stateText}" texts="{texts}" focused="false" selected="false" highlighted="false"
					isTitleClickable="false">
					<zoomLevelOneContent>
						<m:HBox height="100%" justifyContent="SpaceBetween" renderType="Bare">
							<m:Button type="Accept" text="Approve" press="onPress"></m:Button>
							<m:Button text="Reject" type="Reject"/>
						</m:HBox>
					</zoomLevelOneContent>
				</ProcessFlowNode>
			</nodes>
			<lanes>
				<ProcessFlowLaneHeader laneId="{id}" iconSrc="{icon}" text="{label}" position="{position}"/>
			</lanes>
		</ProcessFlow>

Screenshot: