Can no longer connect. Help!

I was just making some progress with HASS and have clearly broken something.

It’s running on my Pi but I cant connect to it. I have static IP set so I’m looking in the right place and can access the config folder using Samba.

The log shows this:

2018-07-25 19:01:47 WARNING (MainThread) [homeassistant.components.http] You have been advised to set http.api_password.
2018-07-25 19:02:00 WARNING (Recorder) [homeassistant.components.recorder] Ended unfinished session (id=16 from 2018-07-25 18:50:51.267122)
2018-07-25 19:02:12 ERROR (MainThread) [homeassistant.components.device_tracker] Unable to load /config/known_devices.yaml: Config file not found: /config/known_devices.yaml
2018-07-25 19:02:16 ERROR (SyncWorker_1) [pychromecast.socket_client] Failed to connect, retrying in 5.0s
2018-07-25 19:02:21 WARNING (MainThread) [homeassistant.setup] Setup of config is taking over 10 seconds.
2018-07-25 19:02:38 ERROR (SyncWorker_12) [homeassistant.components.notify.ios] The notify.ios platform was loaded but no devices exist! Please check the documentation at https://home-assistant.io/ecosystem/ios/notifications/ for more information

Does any of this give any clue as to why? Do I need to rebuild from scratch?

Any help appreciated.

Well the errors relate to device trackers, media players and notify components so, comment them out in the config yaml file and see it you can restart, then add one back at a time to determine where the problem lies.

Thank you for your help. Now resolved. Many, many thanks.