Regarding Technical resignation

Sir, I was In Sate Government service since 21/04/2021, Than I applied for central government service at same pay level. I applied through proper channel, intimated my department while applying for the post, took NOC from department, Than I got selected for that job , after which I submitted my one month intimation letter regarding technical resignation with Lien on 07/02/2024 mentioning last working date as 07/03/2024 , I submitted No Dues also. I also informed my central government department about my previous job, I submitted NOC to them at the time of document verification, Took one month extension period for joining stating about my previous job, but till now that is 15/09/2024 my previous department has not given me relieving letter, due to delay from departmental persons who were dealing my file and I joined my new job as i could not get further extension, kindly tell what can be done , I visited several times to my previous department but every time they say file is under process.