hey actually same thing happened with me.
i am sharing following steps which i did.
kill the running pid by using kill pid command.
then confirm that you have initiated db with airflow db init command.
and created user by using airflow users create command.
after doing this step by step.
use localhost:8080 in place 0.0.0.0:8080.
it worked for me.

mac docker memory issue

I hit this error while developing in my mac, and looking at the logs I found an exited with code: 137, which is an OOM code (although perhaps not always).

In any case, I fixed it by increasing the memory limit to 3GB in docker, following these docs:

By running kill -9 PID resolved the issue

Note for macOS users who runs Airflow via k8s:

In order to be able to see UI up and running on your browser at http://localhost:8080/, you need also to run port forwarding: kubectl port-forward POD_ID 8080:8080

If you’re running Airflow in a Docker, then killing the PID won’t help, neither restarting the service. What you need to do is to search for the Docker container of Airflow’s webserver and remove it like this:

docker ps

CONTAINER ID IMAGE … PORTS NAMES

25d9df23d557 apache/airflow:2.3.2 … 8080/tcp airflow-webserver

docker container rm {airflow-webserver}