XVR Reading Power supply Control Word S1720

We had a XVR on a sercos network with couple of XMD drives.  we added XVR as Sercos IO. We mapped S1720.0.2 but it reads 0. it does not update the data. any comments?

we will try to read parameters via PLC function block.  in any case, not sure why it will not read the data via IO mapping. 

Thanks for the help