Security deposit not returned [NJ]

So we rented an apartment in NJ for almost 2 yrs. after we have finished the 1st year we have signed a new lease agreement for another year but after about 2 mos there were changes in our plan regarding work so we asked our landlord if we could still convert our lease contract to month-to-month basis as we were thinking of moving to a different state. Our landlord sent a request to his managers and eventually said it was approved. So we paid an additional premium fee of 150usd on top of our monthly rent. However, the landlord did not send us a new lease agreement stating the changes. Now we have left the apartment in march 2026 to transfer to a different state. It is now June and we still have not gotten the security deposit that is around 3,900 usd. They have sent the check around May, but it returned to them because the new address my husband sent did not have an apartment number. I have corrected the error the same day the landlord has told me that the check was returned to them. (Note that the landlord does not really respond right away unless you give him a call.) that was on May 18, after that conversation, the landlord was no longer giving us an update. On June 2, I messaged him and he said the person responsible to send the check is out of the country but will return the next day and he said he would get back to me. About 2 weeks have already passed and he still hasn’t returned to me. I have tried to call him but he no longer answers the call. What should I do?? Pls help. :(