As it has been over a year, please politely approach your former company seniors who are relevant. Find out from HR what happened. Please ensure you have properly handled the charge and properties. If you were involved in Sales, check if there are any outstanding amounts from clients under your responsibility. If so, you need to discuss this with management and provide an explanation. I believe there may be pending issues that need attention. Please verify this for yourself first.
Reflect on Previous Communication
Did you ever send an email or letter to the management before? If not, why did you remain silent? Reflect on your reasons.
Confirmation of Resignation
Do you have any written confirmation of your resignation acceptance and did you receive a conduct certificate/experience certificate upon leaving?
Once everything is clear, email all relevant parties and request expedited payment/settlement. Send a registered AD letter as well.
Consulting Legal Advice
After completing all necessary steps, such as meeting in person at least 2 or 3 times at different levels and assessing the situation, consider consulting a good lawyer to handle your case. Agree on a fee percentage once you receive your payment/full and final settlement (as a last resort).