New DP/PA FDC-157-0

I need your help..

Scenario:

There is an existing DP/PA FDC-157-0 (6es7157-0ac83-0xa0) suddenly lightning strikes the plant and all PA devices monitoring are gone. DP/PA module has only "ON" Led lit. So we decided to replace it a new one with part number 6es7157-0ac85-0xa0 (successor of FDC 157-0). My Questions are:

1. Why the NEW module indicate only an "ON" led knowing that there is a PA devices connected to it? All other led are off. 

2. How do i know if my DP/PA FDC157 (6es7157-0ac85-0xa0) is faulty?

Thanks.ASAP reply please :'(

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Split from connect with DP/PA link.