Optional Excerpt Has Stopped Working When Theme Changed

I have been using the Optional Excerpt with no problems for the past month or so. But this evening when I changed my theme the Optional Excerpt does not work at all now.

I know it should work with this theme because it works on this site:
http://www.rspwfaq.com/

My theme is the exact same as that one.
http://www.eastlondonpromotions.co.uk/deansaliba/

Does anyone know how I can fix this?