All that Gloria could do at the bar at Veronaville Market was juggle glasses. . .
. . .which is odd when it evidently worked in base game. Maybe Maxis broke it in Nightlife or OFB. Or maybe I've got some hack that's stopping it working. Whatever it is, my adult Sims can't make drinks at that bar in Veronaville Market! If I want them to, I'll either have to get that hack that was linked to earlier (by Annaminna in post #33) or buy a different bar.

(Gloria had gone across to the Market with Andrew and Ryan Matthews, a townie from Bluewater that Andrew had brought home from school. Disappointed that they couldn't get a drink, and realising that they were hungrier than they were thirsty, they took a cab downtown and had a nice slap-up meal at Oresha's. I always like an excuse to play my original family -- I suppose they really are my favourites. :lovestruc )

On the subject of teens tending bars, I realise, when I think about it, that my founding teens in my island 'hood have a Party Hardy Open Bar (from Celebration! Stuff) on their terrace, and they never have any difficulty serving drinks. (They live in the Abode de l'Amour house that come with Celebration!.) I don't think I've tried teens serving drinks on a community lot yet, but they can certainly drink there. If they are drinking alcohol (a subject on which I prefer to remain vague), then there's loads of under-age drinking goes on in my game!

I don't think it is a hack. I think it is fix what Maxis forgot to do. You can also try if it fixes accessing drink from both sides.