Shopify OAuth refresh token invalid_grant — What it means & how to fix it

Building Shopify apps with OAuth 2.0 often involves dealing with refresh token failures, typically manifesting as the "invalid_grant" error, which disrupts processes like order handling and inventory synchronization. These errors arise when a refresh token becomes invalid, expired, or revoked, often due to using stale tokens after rotation or when refresh tokens expire due to inactivity. The guide provides strategies to diagnose and resolve these issues, suggesting practices such as confirming the use of the latest refresh token, ensuring correct refresh requests, and managing token refresh concurrency. It emphasizes the importance of addressing "invalid_grant" as a token lifecycle issue rather than a transient network problem, and advises on implementing a secure re-authentication process when necessary. Additionally, the text mentions Nango, an open-source API auth tool that simplifies managing token lifecycles for Shopify API integrations by handling refresh pipelines, thus allowing developers to focus on product features.