It looks like you are going to add another barb hook to the tab.
The preview looks like the resulting surface entities cross each other, which won't develop a solid item.
Are you giving it a depth? It may work better to select the Up-to surface rather than Blind as there could be a tiny round-off error between the thickness you think you have and the thickness the geometry actually has. Alternatively, for debugging give it a depth twice the tab thickness. I say this as it appears there is a slight angle to the tab, so room for that error to occur.
