Hi, sorry but this is not related to SLIMax Manager or software support, you should contact your hardware supplier. However, I can try to reply to your question, check if you have only ONE ground for all buttons and open the Encoder tool for SLIPRO and check if an encoder is set at this position.
Hope this helps but as I said check with your hardware supplier, this forum is focused on EKSIMRacing software support.
Cheers,
z