Moving this discussion to the Photoshop Elements forum.
Sometimes catalog conversion fails. It’s often a question of needing full permission settings and the easiest way to make it work is as an administrator directly from the desktop which bypasses the welcome screen background processes.
Make a shortcut for organizer as follows:
On Windows right-click anywhere on the desktop and choose New >> Shortcut
Browse to Computer OS C:
Find the PSE Organizer application in Program Files or Program Files (x86) on Windows 7 - 64 bit.
C: >> Program Files (x86) >> Adobe >> Elements 11 Organizer
Within the Elements 11 Organizer folder find the application PhotoshopElementsOrganizer (not Photoshop Elements 11.0)
Select (highlight) PhotoshopElementsOrganizer and click Next
Then click Finish.
Now right-click on your new desktop icon and choose “Run As Administrator” Then authorize by clicking yes in the User Account Control dialog.
From the Organizer menu click:
File >> Manage Catalogs
Then click the “Convert” button
Select your desired catalog from the list of previous versions of PSE to highlight it then click the “Convert” button down below it
You should receive a message when the conversion has been successfully completed and your earlier catalog will be automatically re-named. Choose the new name from the list and click the “Open“ button and you are good to go.
Please try once again by clicking "Show Previously converted catalogs" checkbox in File >> Manage Catalogs >> Convert dialog.
If this doesn't list your se8 catalog, please do a search for "catalog.pse8db" on your hard disk. The default location of catalogs %programdata%\adobe\Elements Organizer\Catalogs.
Once located, you should be able to get this converted to PSE11 catalog from within Organizer.