Could you please check the Photoshop version? In Photoshop, please go to the Help menu and select About Photoshop... In the dialog, it will say "Version" followed by the version #. The Reflow PS Plug-in is activated in Version 14.1.
If you have a lower version, such as Version 14.0, please close Photoshop, and open the Adobe Creative Cloud application and click on the "Apps" tab. If you see an Update for Photoshop there, please install it. If not, please quit Creative Cloud (select the "gear" icon in the upper right of the Creative Cloud and and choose Quit Creative Cloud). Then restart Creative Cloud, and hopefully the Update for Photoshop will be available.
If this doesn't resolve the issue, please respond here and we'll look for another resolution. Sorry it's not working for you right away!