Not enough info, there's a few ways this quest can go down. If you made the intimation meat, when you enter the wgs hall just stand at the door and wait for him to stop talking, stay hidden. --- I'm Trying to Fly to the Moon Using Two Magnets and Willpower.
But did you go to the oven and pressed A to cook? Also, did you bring "meal" they were going to originally eat? Lastly, did you go to the intercom to tell the waiter to bring the food you prepared?
When you've done all that, you should hide and wait till the speech is over. I had to sneak my way over to Mortimer and talk to him, which would then complete the quest. Otherwise, you'll need to go to the intercom and tell the waiter to serve the drugged wine and then you can just walk out with the "meal." --- If you're messaging me about a dog I really have no idea, sorry
Also, if you cooked the imitation meat there is no need to drug the wine. Not sure what happens if you do both, but when you talk to the waiter just bring up the imitation meat and leave the wine if possible.
I have no idea then. If you have a save file from the middle of the quest or before you made the meal, you could try it again and see if that fixes it. Mortimer should start giving a speech after you enter the dining room area, and as soon as he finishes that is when you approach him. What does the last journal entry say for the quest?