First check whether they are eating enough, not whether they are obeying a feeding rule. A dog who accepts food from your hand may dislike the bowl or its location, seek your company, or feel unwell. A new pattern, weight loss, vomiting, mouth pain or reduced appetite deserves a vet check. Puppies and dogs with medical needs may need faster advice. Do not withhold food to make a point.
Offer the same food in a stable dish in a calm place, and watch whether the dog eats when you sit nearby without feeding each piece. Try an easy container if a noisy or moving bowl may be the issue. Keep other pets separate at mealtimes. The article on mealtime food guarding helps if another animal or person approaching the meal changes your dog's response, but hand-feeding alone does not diagnose guarding.
If your vet considers the dog well, you can place a few pieces in the bowl while remaining nearby, then reward comfortable eating without increasing pressure. Avoid repeatedly switching foods or adding rich extras. Record what the dog ate, where and with whom. A qualified reward-based professional can help if the routine is tied to distress, but food intake comes first.
Today, offer the usual meal in a way they will accept and record what was eaten, then arrange a vet check if intake has changed. A gradual change is safer than a hunger contest.
Sources: VCA on assessing dogs who refuse meals, VCA on appetite loss, Dogs Trust on feeding routines.