On changing the Report Status to 'Published' the report will be locked down, and you won't be able to:

• Change the status; or 
• Make any further edits to the content of the report when you open it in the Report Editor.

Should you find that you do need to edit a published report, you can clone the published report from within the Client & Report Library. This will create an exact copy of the published report as another version, with a status of 'Initial draft', which you can then edit.