Dataverse can assign/use different control types based on the data type of the column it is linked to. It can use Dropdowns, Comboboxes, Toggles, and Checkboxes I believe.
In Power Apps
First I would go to the data section and and check that the data source and the field that is bound to the control is in fact your yes/no column from your DV table.
Also can make sure that the items property is referencing the yes/no column as well. Something like:
YourDVTableName.YourYesNoColName
At this point try saving and previewing the app again to see if it uses toggles instead.
In Dataverse
Make sure your data type is set to two options for yes and no
Check the format settings for that column and see what control it says it will use
Check the default control
Make sure to refresh/reopen your app/form after these changes to see if the change actually worked or not.
