custom theme not appearing

Posted this in another thread but had no reply, so...

Have followed the guide for using a custom theme to the letter and even attempted some tweaks but I can't get it working. End result is either a black square where the player should be, or the dark player skin appears but the player doesn't work.

Default skins work fine with the original code, so there are no problems with the player when any of those skins are selected. I have:

Kaltura 6.x-1.4 with everything enabled including dependencies
Drupal 6.14.

Are there any settings in the management console or app studio I should look at? E.g. a checkbox somewhere saying "make theme public" or whatever? Any obvious/essential changes to settings in Drupal or Kaltura? (Note - I didn't install Kaltura myself so this is a possibility.)