I decide to start a new inquiry.
Could you please to tell me why in some assemblies the New Alternation Icon is blank ?
I spotted that in a few ASYs.
It is disabled for various reasons:
To expand upon Greg's response:
When you open alternate/Family of assemblies from a drawing or a higher level assembly, it will only open that instance or child member and will not allow you to edit any or all other members. If you want to edit all members close the file and reopen it via the open dialog box. Now these icons should be available.