Same problem happened.( Getting invalid_grant error when trying to refresh token)

I had the same problem with the following topic.

What are the possible causes and solutions?

Welcome to the Developer Forum, @naotoshi.nishijima – thank you for posting! Generally, this error is triggered when the latest refresh token is not used in the request. To start, can you confirm if you are using the latest refresh token? Please note while a refresh token is validated for 15 years, it can only be used once.