Unable to Generate complete Audit Log report of previous one month events

Hello Everyone 

I am currently working on SharePoint 2010

I am trying generate Log reports via Audit Log reports option in Site Collection settings, Audit Log report duration has been set to past 180 days in both Site Collection and Central Admin.

When I am trying Audit report I am getting Events data of previous 2 weeks only, My Client needs Data of past 2 months or more than that but Audit logs are failing to collect it in reports, Please help to get it resolved.

Thanks in Advance :)