16 Jul 2012
26 Jan 2011
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Without more information, it's difficult to answer this question but I'll try my best. I create and add new Themes everyday in the official release of Sitefinity and I don't have any issues.
Let's say you have a Theme names 'Spring' in the App_Themes folder. You structure should look like this :
Then you go to Settings - > Advanced -> Appearences -> Frontend themes-> Create new ->
In the Name, type Spring
In the Path, ~/App_Themes/Spring (assuming your folder is at the root directory)
Click Save Changes
That should do it... Let me know if you still can't find it...