Facebook Messenger OAuthException错误：无匹配用户问题解决及疑问

That (#100) No matching user found OAuthException with subcode 2018001 is a clear sign your bot's access token lost its valid connection to your Facebook Page. Even though you used the same token for months without hiccups, here are the most probable reasons it went kaput unexpectedly:

• Underlying User Token Expiry Broke the Page Token
  Facebook Page Access Tokens are tied to the User Access Token of the person who created them. Standard user tokens expire after 60 days, and if you didn't set up automatic token refreshing, the linked page token can silently become invalid over time. Even long-lived page tokens might get revoked if the original user changes their password, enables 2FA, or has their account flagged for security.

• Accidental Permission or Association Changes
  Maybe someone with access to your Page or App Settings accidentally removed the bot from the page's connected apps, or modified the app's role on the page. If that link between the app and page is broken, the old token can't authenticate anymore—hence the "no matching user" error (since the token can't find the page it's supposed to act on).

• Facebook's Security Systems Revoked the Token
  Facebook's automated security tools might have flagged the token for suspicious activity—like unusual API call volumes, or detecting the token was exposed in an insecure place (like a public repo). To protect your page and user data, they'll automatically revoke the token, forcing you to generate a new one.

• App/Page Status Changes Invalidated the Token
  If your app went through a re-review, or your Facebook Page was temporarily restricted (even briefly), the existing token could get invalidated during that process. Once the app/page is back in good standing, you need a fresh token to re-establish the connection.

Generating a new Page Access Token like you did is exactly the right fix here. To prevent this from happening again, set up an automated token refresh flow using Facebook's Graph API, and periodically double-check your app's permissions and page associations to catch accidental changes early.

内容的提问来源于stack exchange，提问作者Stan Wiechers