FNF is not released by the company

I was working with a company in Noida (U.P.) as a data analyst from oct 2019 to jan 2020. I left the company because they were not paying me on time, like first month salary was credited in last week of nov. and similarly they were paying lately while joining HR has told me that the salary will be credited by 10th of every month. I left the job as the project is completed and My senior has promised me they will release the fnf within 45 days but since then they are giving me false promises as the company is closed because of lockdown then they told me that the client is not paying. whenever I called them they give an excuse. HR is also changed and I don't have the contact details of new HR. My last month salary is stuck in FNF. My salary was the only source of income. And in this tough time I didn't have a job and my honestly earned money is also stopped my the company. Please suggest me the legal ways to get my money. I have salary details and joining letter and a promising email from my senior who promised me the amount will be paid in fnf.