I just tested this on my game but it was a different quarter .. romance festival and it was no issue.
Do you travel there after it's supposed to have started or does your Sim live in the area/you're there before ?
My sim lives in another town. The first time I noticed the bug, the festival had already begun when my sim arrived, and another time I tried being on the lot before receiving the notification for the festival. It didn't change anything, the festival wouldn't show up.
I could receive invitations from other sims to go to the festival (whether I was already there or not). The "event" from accepting the invitation starts, but the festival never appeared.
I will try with the same restaurant on another quarter to see what happens, will be back.
I think the problem mainly occurs when the restaurant is owned by a sim (played or unplayed).
I went to the romance festival and it was there, but then I made a sim buy the restaurant, then there was no action at all at the festival (see pictures). Even the stalls had no employees. They were all going to the restaurant (they stayed in front of it because my restaurant was too big for the lot and I didn't notice there was no stairs). The festival was still there though, but it wouldn't disappear (didn't receive notification for the end of the festival either).
Then I sold the restaurant, went back on the lot, (it was around 3 am) and there was an employee in a stall, a sim playing an instrument, sims shopping at the stalls, etc. But the festival wouldn't disappear.
Interesting.
Don't have time for further testing atm but will do so in the coming days.
I have the same issue in the Fashion district. I have a retail store there. If the store is owned by one of my Sims the festival wont appear. If the store is owned by the game then the festival will appear.
