I had the same problem. I needed to add an internal_url and an external_url in my config under the homeassistant: section. Then restart HASS so that config is reloaded. After that the app worked again.
I had the same problem. I needed to add an internal_url and an external_url in my config under the homeassistant: section. Then restart HASS so that config is reloaded. After that the app worked again.