Promotion during maternity leave

Presently i am working as Scientific officer-C in a central government psu NPCIL Atomic Energy department where i joined as SO/C (5400 Grade pay) in2017. i was promoted from SO/C to SO/D joining date was 1 July 2020 and the order to this effect was issued in January 2022. when i was promoted by my office, i was on maternity leave w.e.f. 22 June 2020 and i was blessed with baby boy on 23 June 2020. My office seniors said that as I was on maternity leave, I will not get benefits of promotion wef order issue date. As per them, once I will join the office my promotion benefits will be effective for that date only. i understand that maternity leave is a kind of leave which contains all sorts of benefits to the women employee in the manner as it should be for the person who is in continuity of the service. in view of the above, i would request you to kindly provide me copy of the related rules, regulations and oms for central government employees, so that i may pursue my office to get the promotion benefits and other dues with the due date i.e. 01 July 2020 accordingly .