Instagram error 100: Page is not linked to an Instagram account

Subcode 2534013 means the Facebook Page ID in your call has no Instagram professional account linked to it. Meta's documented note is direct: "The Page ID used in your API calls must be for the Facebook Page linked to your Instagram Professional account." On the Messenger Platform route every Instagram messaging call is addressed through the Page, so an unlinked Page is a dead end regardless of tokens or permissions.

Two distinct situations produce it. Either the link genuinely does not exist - the Instagram account is personal rather than professional, or was never connected to this Page - or the link exists but you are calling the wrong Page: businesses with several Pages, or agencies managing many, routinely send with Page A's ID while the Instagram account hangs off Page B. The companion symptom during onboarding is an empty instagram_business_account field when reading the Page, which is the same condition seen from the other side.

Note that the newer Instagram API with Instagram Login removes the Page requirement entirely; if a Page link is not viable for the business, that route is the structural fix.

Assert the link during onboarding - read instagram_business_account from the chosen Page and block completion if it is missing - and re-assert it on a schedule, because anyone with Page access can unlink at any time without your app being told. Store the Page-to-Instagram pairing you validated and alert when it changes. This is step 1 of the checklist in the troubleshooting guide; the two routes' differing account requirements are compared in the limits reference.