@jitsu87​ Make sure you have the correct version of the sworldswaf.dll that matches both your version of Smallworld and also the bit version (32 or 64 bit) of FME you have installed. More details on the Smallworld configuration here.

Probably worth mentioning the performance issues if you're using Smallworld 4.3 - While you're getting things from GE, they can provide a patch to resolve the problem.

More handy tips on common errors etc. can be found here. (You can ignore the 64bit incompatibility statement and refer to the Smallworld config article mentioned above.)