If you have verified your eligibility for voluntary retirement under NPS through the Railway Establishment Rules 2014 and the statement made by the Honorable Minister Anurag Thakur in 2019, then you have a strong case for seeking voluntary retirement.
However, it is important to note that in some cases, the railway administration may require additional clarifications or documentation before approving a request for voluntary retirement.
In this case, since you have already approached your office and verified the matter through RTI from DOPT, but have not received a satisfactory response, you may consider seeking the assistance of a legal professional or a labor union to help you resolve the matter.
Alternatively, you can approach the higher authorities of the railway administration, such as the General Manager, to escalate the issue and seek a resolution. You may also consider filing a writ petition in the High Court if you believe that your rights are being violated.