If the prudential stock is in the decedent's name alone, it might be necessary for someone to be appointed executor or administrator of the estate to sell or transfer the shares. Typically, someone must be formally appointed by the Register of Wills in the county of the decedent's residence to transact on a decedent's assets. There are some exceptions of course, but this does not seem to be one. You should talk to the legal department at Computershare or Prudential shareholder services for exact transfer/sale requirements in the case of a decedent's estate. This will help you determine the next steps toward resolution.
You may not have found Mr. Kuane's answer helpful, but unfortunately as long as Computershare knows that the registered owner is deceased, it will not re-register the stock without (1) an original death certificate, (2) a short certificate showing authority to authorize the re-registration, (3) a medallion guaranteed signature signed by that authorized person on Computershare's own transfer form, and (4) an affidavit of domicile regarding the decedent.
Probate is just not that onerous or expensive a process in Pennsylvania and if there are enough shares involved, it's certainly worth a trip by the executor to the local county's Register of Wills office.
Feel free to contact me if you need assistance.