Do you use mods? If so, remove your Mods folder and see if you have better luck. If not, then do a game repair and see if that helps. I love taking my Sims out to dine and have also had moments where it just utterly failed. When I tried to set up a Date, as in prior to Lovestruck, I had the problem of not being able to request a table. Even Carl's Dine Out Reloaded mod wasn't helping. What I do now is have one of my Sims ask their sweetheart to create a date. Dining out isn't fully functional, as before, but they do get a table. If you take them to a bar, they can get food, at least.