Add I/O module to S7-1200

Hi all,
I've got a S7-1200 ( 1215C ) and I'm wanting to add a I/O Module to it a SB 1223 DC/DC the small 2 in 2 out module that plugs in the front of the CPU, all was going well I get a red warning ! saying error in low level component and the component is saying not reachable , any ideas as to the cause of this?

Thanks in advance

Worked out what was wrong , I'd missed compiling the hardware changes. D'oh