Howdy!
We changed the way Ganged Electrical works in X17. In previous versions, these blocks were created automatically when switches/outlets were within 9" of each other. Now, these blocks get created as the result of multi-selecting the Electrical objects and clicking the "Make Ganged Electrical Block" action on your edit toolbar.
When you load in an X16 plan that has the old Ganged Electrical, we automatically convert them to the new version. This is the only time the new Ganged Blocks are created automatically.
Hope this helps!