1. Did you work in India or USA?.

2. Assuming that you had worked in India, then you are entitled for gratuity.

3. Since you had availed 5 months' maternity leave, 5 months' LWP and 5 months' LWP for Childcare with specific sanction from the competent authority, i.e., from Reporting Manager and HR, the period of leave has to be considered as continuous service and not as break-in service.

4. In view of all these sanctioned leave from the Competent authority, your absence will have to be considered as continuous service and cannot be considered as break-in service. To qualify for break-in service, an employee should have absented for duty without obtaining proper sanction for availing leave.

5.  To conclude, you are entitled for gratuity and if you are denied gratuity by your employer, send a legal notice and wait for positive response from your ex-employer. If there's no positive response, file a case against your ex-employer with the jurisdictional Labour Commissioner/Labour Court.

under the provisions of Payment of Gratuity Act, continous service includes all kinds of leave unless by an express order there is break in service. .

.. 2) Leave Without Pay, being sanctioned leave will be treated as part of 240 days for calculating eligibility for Gratuity.

That is ridiculous. It cannot be a break in service. Serve him with a legal notice.

The opinion of the employer that the leave without pay would be considered as break in service is incorrect.

 As per Section 2A of the Act, it is clear that in the event the employee is absent from the duty due to sickness, accident, leave or absence from duty without leave, he/she would be entitled to the benefit of gratuity unless the employer has passed an order treating such absence without leave as a break in service in accordance with the Standing Orders of Employment applicable to the employee.

In the case of a sabbatical leave, the same would essentially qualify as a leave if permitted by the employer and would only be a leave for a longer duration than a usual leave and therefore, it shall be treated as a continuous service in terms of Section 2A of the Act.

In other words, if an employee goes on a sabbatical with the consent of the employer and resumes work after completion of the period of sabbatical, he or she would be deemed to be in ‘continuous service’ for the purpose of payment of gratuity.

You can make a representation i writing to the employer by referring the relevant section of law which has been cited and seek his intervention  with desired relief.

If there is relief provided you may initiate proper action as per law against the employer.

your employment contract will have to be perused to check how the gratuity is to be computed and what all deductions are permitted and what all is considered as break in service thereby disentitling the employee from the gratuity benefits

without the employment contract/terms in the letter of appointment, it is difficult to comment 

File a complaint with labour commission or file a suit before labour court