With this error message, Gerrit rejects a push of a commit to a project if the commit message of the pushed commit contains a Change-Id line that is not in the footer (the last paragraph).
To be picked up by Gerrit, a Change-Id must be in the last paragraph of a commit message. For details, see Change-Id Lines.
You can see the commit messages for existing commits in the history by doing a git log.
Change-Id is contained in the commit message but not in the last paragraph
If the Change-Id is contained in the commit message but not in its last paragraph, you have to update the commit message and move the Change-Id into the last paragraph. How to update the commit message is explained here.
To avoid confusion due to a Change-Id that was meant to be picked up by Gerrit not being picked up, this is an error whether or not the project is configured to always require a Change-Id in the commit message.
Part of Gerrit Error Messages