To-do bot needs to be in the space for you to create a list.
If you are unsure if to-do bot is in the room, you can click on the person icon to see the list of below (below):
In the space where to-do bot is located, type @to-do list and press enter.
The to-do bot has to be mentioned correctly when it is highlighted in blue as below.
The to-do list is shown in the space