The route may be familiar, but the walking group has changed. That can make the outing feel different even if both people are trusted. Do not pull a dog who plants their feet, and do not decide they are being stubborn from one refusal.
First check whether the dog seems sore, tired, afraid of something on that route or reluctant to walk with either person in other settings. A sudden change in willingness to move needs veterinary advice. Use a short, safe toilet plan today rather than forcing the full loop.
At an easy time, begin with both people together. The person who will walk alone can handle the lead and reward comfortable steps. The other person can turn back while the dog is still relaxed, leaving a short route with a quick way home. On another day, start even closer to home if that was hard. Avoid making a solo walk predict being pushed through a long route. The loose-leash walking guide may help with lead skills, but the important question here is how the change in company affects this dog.
Today, note where the dog stops and whether the same place feels easy with both people. That comparison can guide the next small step.
Sources: Dogs Trust on adapting walking practice to the dog's comfort. VCA on fear of places and not forcing a dog forward.