Original post/thread found here but so called Community Specialist saw fit to lock it down due to inactivity, which was total b u l l. It might be possible that they missed the recent activity as it doesn't always flow in a linear fashion, with newcomers replying to older parts of the thread.
https://www.googlenestcommunity.com/t5/Nest-Thermostats/Home-Away-Assist-returning-home-always-stuck...
I'll try and keep this simple. What many of us are finding is that Nest Home/Away assist is partly broken. It accurately reports when we are Home or Away, but fails to switch the thermostat into the corresponding Heat or Eco mode. We are also being told by Google that it will eventually switch to Eco between 1 to 3 hours later, in the meantime wasting precious energy heating an empty house or freezing upon your return as it fails to change back to heat. Even worse if people manually switch it to Eco mode on leaving home and then forget to change it back upon their return they will wake up to a cold house as it doesn't auto switch back to Heat if manually turned to Eco.
After going through all the online or telephone support, jumping through the multiple hoops that they keep on demanding we as individuals "need to do" but never getting it resolved in a timely and satisfactory manner.
HOWEVER,
There is a workaround both for Android and IOS from 15.3 Samsung Smart Things (SST) can do the geofencing bit and works very well, once configured correctly. All you really need is the Nest app and SST. Most people report that you don't need to change any of your settings in the Nest app. (Personally I had to turn off Location by phone in the Home/Away assist setting, which in turn means it doesn't accurately report Home/Away status in Nest app, but it can be setup in SST anyway, but the important feature of Heat/Eco switching works flawlessly)
SST effectively replaces Google Home.
Here's a video of my setup think it needs to be downloaded as it doesn't tend to play from the internet...
https://drive.google.com/file/d/1-M67h1ZMgvC18w1TlN9Pgi9mHLcAgsap/view?usp=sharing
In SST you need to add the Nest device hen configure your Home / Away Routines can be for just one person or for many, below is how to set it up for 2 people. The main account holder will have to invite subsequent family members to use SST.
To add Nest Thermostat to SST
Go into SST>Devices>+Add Device>select from list of devices>By Brand>Nest> Select your nest and that should then connect to the thermostat. I'm assuming this needs to be done while you're at home.
HOME ROUTINE
IF +
WHO both your phones listed
WHERE your home address
WHEN, ANY phones or tablets AT your address
THEN+
CONTROL DEVICES, Select your Nest from devices list, then next, Select mode, HEAT
Optional extras
Send notification to members, this will notify you that it has been actioned.
Change this locations mode. HOME
AWAY ROUTINE
IF+
WHO both your phones listed
WHERE your home address
WHEN, ALL phones and tablets AWAY from your address
THEN+
CONTROL DEVICES, Select your Nest from devices list, then next, Select mode, ECO
Optional extras
Send notification to members, this will notify you that it has been actioned.
Change this locations mode. AWAY
Thanks to @Steve59, @Iany1954 , @islandniles, @steve99uk , @jrawle , @BrianDarby , @LifeonMars
And the many other contributors to the closed thread. Hopefully we can keep this one alive until Google pull their finger out....
