Q: Why do I lose my widgets sometimes from theme to theme?
A: Each theme has its own template container names, but they are not always the same from theme to theme. Each theme has its own number of containers. The default themes can have from one to five containers. You also may not have the same number of widgets to work with in a different container. For instance, if you have a theme with three containers and you change your theme to one with two containers, your widgets in container number three will be gone and will need to be added to one of the two containers in the new theme.
Most of the time the widgets in similar container locations will move over into the new theme, but this is not always the case. When you change your theme, do check and make sure the widgets have moved over. If they have not, they will need to be added again.
If some of the widgets from your old theme are showing on your site but you can't see them to edit them, the best course of action is to change your theme back to the previous theme and remove all the widgets. For instructions on adding widgets, see https://www.netadventist.org/new-widgets.