after upgrading to 0.115, i have problems with tradfri. I manage to integrate it but subsequently all modules go offline. installation on hassio
Had the same issue.
Take i look in the tradfri app.
After a new login everything worked for me.
the app on smartphone or where?
Sure, on the smartphone, where else?
the error is:
2020-09-22 12:21:22 ERROR (MainThread) [homeassistant.setup] Error during setup of component tradfri
Traceback (most recent call last):
File “/usr/src/homeassistant/homeassistant/setup.py”, line 213, in _async_setup_component
result = await task
File “/usr/src/homeassistant/homeassistant/components/tradfri/ init .py”, line 59, in async_setup
configured_hosts = [
File “/usr/src/homeassistant/homeassistant/components/tradfri/ init .py”, line 60, in
entry.data[“host”] for entry in hass.config_entries.async_entries(DOMAIN)
KeyError: ‘host’
Ok, one last try: 
Do you have the tradfri hub?
If so, do your tradfri devices work if you manage them with the official tradfri smartphone app?
yes i have the ikea hub.
i logged out the account and then reconnected it. Will you tell me what I’m supposed to do?
only when i delete and reinstate the ikea integration function. if I restart the system all the devices managed by the hub go offline.
I opened the app, it asked me to scan the QR security code on the bottom of the hub again, and all worked as before.
Sorry, that’s all i can tell you.
have you tried restarting home assistant?
Yes, since 0.115, multiple times.
I don’t understand then why it doesn’t keep settings on reboot …