Airflow "This DAG isnt available in the webserver DagBag object "
It is not you nor it is correct or expected behavior. It is a current 'bug' with Airflow.The web server is caching the DagBag in a way that you cannot really use it as expected.
"Attempt removing DagBag caching for the web server" remains on the official TODO as part of the roadmap, indicating that this bug may not yet be fully resolved, but here are some suggestions on how to proceed:
only use builders in airflow v1.9+
Prior to airflow v1.9 this occurs when a dag is instantiated by a function which is imported into the file where instantiation happens. That is: when a builder or factory pattern is used. Some reports of this issue on github 2 and JIRA 3 led to a fix released with in airflow v1.9.
If you are using an older version of airflow, don't use builder functions.
airflow backfill to reload the cache
As Dmitri suggests, running airflow backfill '<dag_id>' -s '<date>' -e '<date>' for the same start and end date can sometimes help. Thereafter you may end up with the (non)-issue that Priyank points, but that is expected behavior (state: paused or not) depending on the configuration you have in your installation.
This error can be misleading. If hitting refresh button or restarting airflow webserver doesn't fix this issue, check the DAG (python script) for errors.
Running airflow list_dags can display the DAG errors (in addition to listing out the dags) or even try running/testing your dag as a normal python script.
After fixing the error, this indicator should go away.