Can't 'Convince to Buy' on Food Stall

I don't think it's a bug. Some aspirations are just unreasonably complicated or illogical. One of my Sims is selling some of her food at a foodstall, too, usually before she goes to work, and convincing another Sim to buy that food doesn't always work because that Sim might walk away. Make sure you don't try to use the interaction on every Sim that approaches your stall because once it has been completed, it greys out for a while before you can use it again. It's really annoying and doesn't make much sense either, especially with high charisma. 

Jehane40​ Aelynsims​ does anyone know the secret of this, because it's really extremely difficult. the sim i played, the super sim challenge sim, the skills at the highest level, the food is of excellent quality. but never the aspiration is complete

This is really strange as I personally have never had a problem convincing to buy, it normally works nearly every time. I don't sell from my home lot though I usually go the park in oasis springs. Maybe it has something to do with the aspiration that makes it harder to do, some programmer somewhere decided to lower the chance on successfully completing a convince to buy. lol. Never tried the aspiration, maybe I will try and see if that's the case, 

Ok, I loaded up a new save to check this and I can complete the convince to buy on my home lot but I am unable to cook anything of poor quality for the next part of the aspiration, everything I cook even at level 1 is normal or excellent quality. I have had 2 toons try this now and they are both the same no poor quality items. It seems a bit daft to put that in the third part of the aspiration anyway as the cooking level is going to be higher by then so  the chance, if there was one, is gonna be practically nil.

even though i had previously made the convince to buy, and even if the customer had bought the food, the counter was not progressing. i changed my sales location and it seems that my problem was solved. maybe i don't know it works if there is someone who has the same problem. i started selling at my house and so it works 

even the food I made with uncomfortable moodled and spoiled fish was of normal quality, moreover, the refrigerator and stove were the cheapest. i found the dish in poor quality by making "dive for meals" although a few times it was spoiled product but I was able to finally find 2 poor quality dishes. billblogs​ 

I completed that part of the aspiration just last night! I also struggled a bit, then I realised that 'convince to buy' works better on Sims who have good relationships with the seller. 

In regards to the poor quality food, I made my Sim bake with several low needs (comfort, bladder, hygiene etc), then I selected a dish at a high skill, like 8 or 9. Came out poor, no problem. 

Hope this helps!