HCL Technologies — Final Salary Deducted due to Timesheet app issue

I have recently received FNF(Full and Final settlement statement) from HCL where 7 days LWP is marked for last week, on last day i submitted timesheet through empower app as i was in office for exit formalities, and that timesheet didn't got reflected in system, now for that week LWP was marked, i did not get any mail for that neither my reporting manager updated that,
so in final salary 7 day payment is deducted,
Now I am seeking solution for this, my HR as well as Reporting managers are saying they acknowledge that i have worked but cant's do anything if timesheet is not there,
I believe in extreme scenarios manager can fill or raise tickets for these things.
i need help on this front as no one is against that i have worked, just no one knows what can be done to correct this.