With status "Audits completed, under generation report" you can change the report part (General information, Overview, Repeated NC, ...), and also re-open audit by click on the blue title of audit to reopen.

Within 2 weeks after audit start date you can reopen an audit if the status of the report is "Audits completed, under generation report" AND :

• if you are the lead auditor or a country user, if the report has been validated once, you cannot reopen the audit anymore. If the report has never been validated, you can reopen the audit. Please go in this case back to the audit checklist by first clicking on 2.2 store inspection date (blue ribbon as shown in the screen shot) 

If the report is already validated and the CAP has never been completed, within 2 weeks, the support/admin user can re-open the report/checklist for you. If the CAP has been completed once, it is not possible to reopen the report/ checklist again.