CircleCI allows users to rerun a workflow for up to 90 days. If you are unable to rerun an old workflow, it's best practice to make sure that the build was originally triggered within the last 90 days.
If you try and rerun a workflow from your pipelines page (that was originally triggered more that 90 days prior) you will not be able to re-run it . You will not see an error message. Clicking the rerun button in the UI will result in no action.
If you try and rerun a workflow from the workflow's page, you will be redirected to your pipelines page and the workflow will not be rerun.
If you try to "approve" a "on hold" job (that is more than 90 days old), you will see no error message and your job will not be approved.