CB version 3.9.1 only supports URCap API versions up to 1.6.x. In this case you either need to use the Starter Package SDK 1.6.x and recompile your URCap, or update the robot to 3.13, or later, which supports 1.10.0.
e-series added the URCap API 1.10.0 in 5.8 which is why those work.