It's not enough to just turn things on in Course Configuration. That essentially _enables_ SMA, but it is still off by default for every single problem. One reason is that with a multiple choice question that randomizes the choices order, you don't want to allow the SMA button where you might give away the answer in the SMA version of the problem.
If your set is live and has had student work already, visit the set details page for the set. Alongside things like "weight" for each problem, there is an SMA parameter. This is the number of attempts a student must make before they can use the button. "-1" means they can never use SMA. "0", and they can use it right away. "13" and they have to use 13 attempts before it is no longer grayed out.
It sounds like you may have set definition files for this set, and apparently they were saved with this SMA parameter set to -1 or not initialized at all (in which case -1 is presumed). So you can also edit the set definition files prior to import to set the SMA property to 0 (or higher).
The set definition files could be "Version 1" or "Version 2". See here for how to set the SMA parameter: http://webwork.maa.org/wiki/Set_Definition_Files
If any of this is a big pain (like, you have 50 set definition files you'd have to edit), if the set definition files did not specify the SMA parameter, then you may be in luck. You may be able to add a line to your course config file that changes the default -1 behavior to something else. At the moment of import, the new default would be used and written into the database. You could then export the problem sets and they'd get exported with the new SMA paramater and you;d be good for the future.
If you have 50 set def files and they _do_ specify the SMA parameter, you could use regex on them to mass edit the SMA values.