Sef robot.

Hello,
We have a SEF robot With vrs1 control. In our installation there are 2 in/ output cards. However, the plc sees only the first card. We already switched cards, loaded constants. Phisically the card works but the plc does not know that the card is there. Has enyone an idea what the problem could be? The installation has been running for 20 jears and this is the first Time this problem occured. Answers in German is no problem its only difficult to write German on a Belgian keyboard.