Heres a quote from a fellow user that may make it a bit easier :)
4.0 out of 5 stars
Becomes a lot more useful if you change the default manual behaviour via the Tado website
Having tried out this skill I started writing a review similar to many of the other reviews you will find here complaining about the need to change tado back to auto mode via the app. However, while making a suggestion at the end of my review I thought I'd double check one of my suggestions wasn't already possible. I was pleased to discover the default manual behaviour can be changed on the tado website. The factory default is "Until Ended By User" this means - as many have already commented - that you need to use the app, website or possibly the smart thermostat to switch back to auto mode. If you change this to "Until Next Automatic Change" it suddenly becomes a lot more useful.
Here are the steps to change the default behaviour used:
1) Logon to your tado account via the website.
2) Open the side menu by clicking the dot in the top left corner.
3) Select Settings
4) For each zone under the section labelled Manual Control on tado device use the drop down menu to select Until Next Automatic Change.
When set to Until Next Automatic Change tado will revert to auto mode if everyone leaves the house as well as scheduled changes. Alternatively you can set a time you want to apply the temperature change for. From what I can tell this doesn't affect the tado app. The app still remembers your last selection. I'd recommend tado place these or similar instructions in the description for this skill.
Having said all that there are still a few features missing from this skill that would be nice. I'd like the ability to turn the heating completely off and tell Alexa how long to apply a temperature setting for.