The installer program for Photoshop CC 2015.5 does not copy plug-in files used in previous versions of Photoshop to the new version. If you have the DxO plugins for FilmPack and ViewPoint installed for an earlier version of Photoshop, you can use these instructions to move the plug-ins to Photoshop CC 2015.5.
Without Photoshop running, go to the plug-in folder of the previous version of Adobe Photoshop. On a Mac, this folder is located inside Macintosh HD/Library/Application Support/Adobe/Plug-ins/CC. On a PC, the path is Hard Drive\Program Files\Common Files\Adobe\Plug-Ins\CC.
Next, copy the DxO plug-in folders you find to the plug-in folder for Photoshop CC 2015.5. On a Mac you can find the folder at Macintosh HD//Library/Applications/Adobe Photoshop cc 2015.5/Plug ins. On a PC, the folder is located at C:\Program Files\Adobe\Adobe Photoshop CC 2015\Plug-ins.
Now, when you start Photoshop CC 2015.5, the DxO plug-ins you used in the previous version of Photoshop should work with the new version of Photoshop.
Adobe has a Help page devoted to plugin issues customers are experiencing with Photoshop CC 2015.5. You can find this page at https://helpx.adobe.com/photoshop/kb/plug-ins-photoshop-troubleshooting.html