On open lists, you are only able to change the status of items that you have created. This is why you may see the status buttons disabled and greyed out.
When creating a list you will see the option to choose a status group, see Using custom status groups. By default the list will use the 'Progress' option which allows you to track the progress of your items with the following status':
– Incomplete (default status after an item is created)
– In progress
Your items will also end up as a 4th status if they become overdue and they are not yet set as complete. In this case, they will automatically show as Overdue (this applies to all custom status groups too).
To change an item's status (the examples below are using the Progress group as above)
1. Go to the list for which you would like to update the item status.
2. Swipe an item which you like to change the status of to the left.
3. Tap on the new status to change it.