Make sure that both the following settings are on:
Self Manage Payroll
Enable Internal Pay Runs.
Check the timesheets for alerts.
Make sure that you can Approve and Authorise the individual timesheets.
Check the Location Access for your user.
Make sure you've checked the Exact permission groups assigned to the User in the Employees screen. To be able to Commit to or Submit to Payroll you need an appropriate Permission Group for that Location:
Check the Permission Group for your user.
If you are using a custom Permission Group rather than the built in permission groups, check your permissions.
In the Settings > Permission Groups screen, make sure that the group in question has a tick for the Payroll Management box:
This is the permission that ultimately controls whether you are allowed to Commit/Submit a timesheet to Payroll.