backend does not start

docker-compose up -d starts each one of the services, but backend service fails with the following:

docker-compose logs backend

Attaching to iaas_backend_1
�[36mbackend_1        |�[0m Checking for script in /app/prestart.sh
�[36mbackend_1        |�[0m There is no script /app/prestart.sh
�[36mbackend_1        |�[0m INFO: Uvicorn running on http://0.0.0.0:80 (Press CTRL+C to quit)
�[36mbackend_1        |�[0m INFO: Started reloader process [1]
�[36mbackend_1        |�[0m ERROR: Error loading ASGI app. Import string ":app" must be in format "<module>:<attribute>".
�[36mbackend_1        |�[0m INFO: Stopping reloader process [1]

I tried to get into the backend's bash to try debugging, but it also fails:

docker-compose exec backend bash

ERROR: No container found for backend_1