title: Airflow 2.1.0 - DAG 'XXXXXXXX' not found in serialized_dag table
body: <p>We recently upgraded from Airflow 1.10.12 to Airflow 2.1.0 and are getting issues errors like this in the UI for each of our dags.</p>
  <p>We have upgraded the version from 1.10.12 to 1.10.15 and it was successful. Then from 1.10.15 we have upgraded to 2.1.0 and facing this issue.</p>
  <pre><code>File &quot;/home/airflow/.local/lib/python3.6/site-packages/airflow/models/dagbag.py&quot;, line 249, in _add_dag_from_db
      raise SerializedDagNotFound(f&quot;DAG '{dag_id}' not found in serialized_dag table&quot;)
  airflow.exceptions.SerializedDagNotFound: DAG 'XXXXXXXX' not found in serialized_dag table
  </code></pre>