There are 2 things which may be causing an issue here:
- Widgets can be controlled for each area. If your area settings don't have "Widgets shown in this area" set to "Any block", then you need to apply your new widget to the area manually.
- Wiki widgets can be tuned using Widget permissions. In AdminCP > Appearance > Widgets, you should see a button near the top "Widget permissions for Wiki". Here you can specify which groups are allowed to see the widget. However, my reading of the code is that all user groups are automatically granted access to a widget when you create one, so there shouldn't be any issue here.