People often think recall training begins by calling a dog from far away. It usually works better to begin at a distance where the dog is almost guaranteed to succeed.
Make coming back easy
Call your dog from only a few steps away. When they turn toward you, reward generously. Repeat until the response becomes quick and automatic.
As the behavior becomes reliable, gradually increase distance and distractions. Each successful repetition teaches your dog that responding to the recall cue is worthwhile.
Don't turn recall into a trap
One of the fastest ways to weaken recall is to use it only when something fun is about to end. If every "come" is followed by the leash going on, the walk ending, or an unpleasant activity, your dog has a reason to hesitate.
Practice recalls during good moments too. Call your dog, reward them, and then release them back to whatever they were doing.
Reward the response, not your frustration
Even when your dog takes longer than you'd like, reward them when they finally come back. The useful information for the dog is that responding to the cue still pays.
Recall should be one of the most valuable behaviors in your dog's repertoire. Build that value deliberately, long before you need it in an emergency.