I recommend you review the materials on the responsibilities of SSA Representative Payees at the SSA's website. The link is below.
This is not a substitute for a consultation with an experienced Social Security attorney or advocate.
You would have to be appointed with a special SSA power of attorney or be appointed as guardian before you would have any power to accomplish anything for the recipient.
The answer given does not imply that an attorney-client relationship has been established and your best course of action is to have legal representation in this matter.
Your question is not clear. If the payment was rejected, then the payment would revert to the SSA. Only they could reissue it to a different payee.
Actual legal advice can only be provided by an attorney licensed in your jurisdiction, with experience in the area of law regarding your question. The information provided is for informational purposes only and is not legal advice.