Siemens Logo 8, Modbus connected but no IO

I`m working on a robot bending application and i needed more IO.
My first thought was a full blown PLC but i figured i would save cost and buy a Siemens Logo 8
The Logo 8 supports modbus which i could use for the IO and it also has a webclient to get some online monitoring in place.

I connected the Logo to the robot and after setting it as the modbus server i got a green dot on the robot connection status.
But thats were it ends. I cant get the digital IO to communicate one way or another.

Anyone have experience with this, or got a logo working on there own robot?