I'm not allowed to edit on my listing. Why?

Your Broker will need to give you Add/Edit permissions.  

http://web1.tulsarealtors.com/gtar2/GTAR/Forms/707.pdf 

Or, if you have changed offices, even branches, the Listing Office of your listing will need to be adjusted and is why you are unable to edit your listing. The Broker will need to transfer the listing to the correct Listing Office that you have transferred to.