Too many changes at once
A cue learned in a quiet room may be much harder beside a busy gate. Change one part of the exercise at a time: distance, duration or distraction. If success disappears, return to an easier version and rebuild from there.
Mixed messages in the household
One person may reward jumping while another expects four paws on the floor. Write a short agreement about greetings, doors and resting spaces. Choose a response that everyone can apply calmly and consistently.
Missing a change in comfort
A dog that suddenly resists a familiar activity may need a health assessment, not a more forceful cue. Record what changed and speak to the vet. Good training notes describe behavior and circumstances without assuming that the dog is trying to challenge someone.
GO A LITTLE FURTHER
Sources & useful reading
AVSAB: humane dog trainingAAHA: recognizing pain in petsA little more understanding. A better everyday life.