Are they on a PPA document?
If the answer is yes you are done, the deadline is 4/30/2016 but it could have been done as early as May of 2014, I believe since that is generally when the preapproved PPA documents first became available.
If the answer is no and they are on an EGTRRA document then they need to restate the plan by April 30, 2016.
Answers above assume Plan is using a preapproved volume submitter or prototype document and is not individually designed.