If a dog hasn't been properly trained to respond to the recall command, they may not understand or recognize it.
Dogs can easily get distracted by their surroundings, such as interesting smells, other animals, or people, which can divert their attention away from coming when called.
Dogs that are fearful or anxious may be hesitant to come when called, as they perceive the situation as threatening or overwhelming.
If a dog has had negative experiences associated with coming when called, such as punishment or scary situations, they may be reluctant to respond in the future.
Dogs may not find the reward or incentive offered for coming when called enticing enough to override their current interests or activities.
Certain medical conditions, such as hearing loss or pain, can affect a dog's ability or willingness to come when called.