@ Nick
The list_type option for the [upcoming_list] plugin sets the template type to load. There are only templates available for anniversaries and birthdays. There is not one available for memberships so this will result in the template not found error you are receiving.
What you can try is setting the template option to anniversary or birthday to override the type set by the list_type option. That said, maybe this code will work:
<div style="float:right; width:410px;margin-bottom:60px;">[upcoming_list list_type='membership' show_lastname='true' list_title='Rotary membership anniversaries in the next 30 days' template='anniversary']</div>
I do not know if that will work as I have never tested this scario before.
Hope this helps, let me know.
