Okay...Did you have a question as you failed to ask one which is a reportable violation of YA guidelines?
Dogs aren't vegan their carnivores, requiring meat, a vegan diet is not suitable for canines, it lacks meat, as well as failing to be specifically formulated nutritionally for a canines dietary needs and is not complete/balanced.
No healthy dog has yet intentionally starved themselves, the dog will eat if you feed it properly and nothing else, other than water which must be available free choice 24/7, it may take 3-4 days before you see an improvement in appetite.
Frequent/sudden diet changes may cause intestinal upsets, including appetite loss. All diet changes should be done gradually over a period of ten days to two weeks by mixing old diet with new diet by two weeks dog should be completely on the new diet, and remain on said diet for the remainder of its life, dogs don't need variety in their diet. The only reason for any diet change would be due to a specific medical issue, and/or if if vet recommended/prescribed.
Keep in mind most vets aren't nutritionist unless they have specialized in nutrition in addition to their regular vet curriculum, and have been certified in that as well. Many may recommend/sell/push other foods, only because they get a kickback from the manufacturer.
Begin by taking it to a vet to rule out any medical issues first, once medically cleared feed it properly.
On a set schedule, total daily set amount, twice daily, am/pm, split equally into those two meals, according to body condition/activity, without exceeding the the total daily amount, water should be available free choice 24/7, food should not be left available free choice 24/7.
No free feeding, over treating, human foods, scraps, supplementation (unless vet recommended due to a specific medical issue), or additives to encourage appetite, period.
Place food down for 5-10 minutes, then pick it up whether it's eaten or not, store properly, offer again at the next meal. Offer nothing else or anything in between or allow dog to access anything, including any food products..
Guaranteed it will eat when it gets hungry enough, if not back to your vet. Good luck.
Should have realized this came from a BFA...