You need to register to become a Sage Developer (currently about £1000 per year). This will then allow you to use the tools already installed with Line 50 (sdoengxx.dll, I think). Until you register, you will have problems using them, from what I can remember.
As a registered member, you also gain access to their online knowledge base which can be useful. I've not done anything with Sage for 3 years now, but I was involved in the development of an app for posting invoices and updating stock levels.