We would suggest putting in a special price code for “Restricted view” seats. That way, they will know, for sure. Those seats would be for sale for only the “Restricted view” price.
Depending on how important this is, there are other things you can do. Adding a popup is probably not going to work. Most browsers have popups turned off these days.
In this example, we’ve made the seats green by choosing Character 232 for its status:
When someone purchases those seating through Webtix, they will see that they have a restricted or obstructed view.