You could have merged verts too, just delete all history and then applied it. Even quicker

Another reason for failure to Sd can be also due to the fact that the base mesh count is too low: eg: the default is 3200 if Im correct, you may get an error saying base mesh is eg 3500 so therefore increase the conversion count to match this or better still increase it further to say 4000. In this case it wasnt the prob but its something to be aware of, for the future.

Regards
Jay