When you're setting up the KOCT offline Circulation Firefox plugin and are configuring it to point to a specific Koha staff interface, you need to have had that Koha staff interface opened in the same browser beforehand. Otherwise the configuration will not be saved correctly and on the first usage it will give an error like "please configure the connection data" or similar. That's not a big problem if you know that you should do that and probably most people will have opened the staff interface in the same browser beforehand anyway. But we should still document it somewhere so that noobs like me don't waste time on it. :)