python thunorctl.py createsuperuseron the command line.
python thunorctl.py version. If not, then run
python thunorctl.py upgrade. Then, make sure you've created an account using
python thunorctl.py createsuperuser. Use the email address and password that you entered there to log in to Thunor.
docker-compose logs appin the thunor-web directory. You should see a Python exception with a Traceback with further information on the error.