Did you send the correct witness fees? Did you send a sunbpoena for deposition or a subpoena duces tecom? Did you contact the recipients to see if they received the subpoena and if there was anything else they needed? Did you send you subpoenas using a clerk's form and to the proper recipients? (You cannot use a subpoena if you are not an attorney unless you obtain and use the clerk's sealed form.) You asked a similar question a while back and were informed that you really should have had an attorney and that you are treading is dangerous waters by trying this case without legal representation.
Agree with Judy. You are involvrd in an area of practice known as discovery that often causes difficulty for lawyers. Be sure that the requirements of the subpoena have been met as noted by Judy.
Contact the recipent and ask about compliance. Ultimately, your recourse may be requesting by written motion, served on the recipient, that the court enter an order compelling production. If you have been diligent, the fact that discovery is closed probably will not prevent you pursuing needed documents. Courts tend to want cases determined on the facts. You ought to at least consult an attorney on the issue.