This error means the Facebook profile that connected your Page no longer has the access it needs to publish to it. It can happen on any plan.
What the error says
Facebook denied CoSchedule's request to send this message for this user. The error message from Facebook said: "The user must be an administrator of the page in order to impersonate it." Re-authenticating this profile may resolve the issue for future messages. You may choose to reschedule this message after re-authenticating.
Why it happens
The personal Facebook profile that connected or last reconnected the Page lost its admin role or full control of the Page, or that person was removed from your CoSchedule calendar. It often follows a change to the Page's admins.
Fix it
- Check that your personal Facebook profile has full control of the Page. Facebook explains how to see your Page role or access.
- If you don't have full control, ask someone who does to give you access to the Page, or have them reconnect the Page instead.
- Reconnect the Page in CoSchedule from a desktop browser. See Reconnect a social profile.
- If the same person connected other Facebook Pages or Instagram accounts to your calendar, reconnect those too.
- Reschedule the failed message.
Prevent it
Reconnect your Facebook Pages and Instagram accounts whenever the Page's admins or the connecting person's password change. Giving more than one person full control of the Page also helps.