Demand Notice retuned with remark addressee left

First, preserve the envelope, and inquire about facts and contact the postmaster and arrange for delivery of the envelope if the drawer still residing in the same address.  If not find out what's app or email address and send the notice.  Any notice served on the nearest relatives (Spouse,parents or children) can also serve the purpose.  Contact advocate and if he feels publish the same in the newspaper.  Inquire with the bank (Drawee) whether there was a change of his address or his cell or e mail address from them, as the issue is related to criminal offence.

the legal principle is that a notice refused to be accepted by the addressee can be presumed to have been served on him. Likewise, once notice has been sent by registered post with acknowledgment due to a correct address, it may be presumed that the service has been made effective, though in such a case, the accused can show that he did not receive the notice. Therefore, if the complainant can prove these facts, the complainant can be presumed to have discharged his burden of service of notice, and then it is for the accused to show that he did not receive the notice.

The notice is "unserved" and returned, i.e., you are yet to serve at the correct address of respondent/accused.