I am using Zenon 6.20 SP1 HMI with a 1756-L61 Allen Bradley cpu(RSLogix 5000 v17). The plc chassis contains both ENBT and EWEB modules for communication and these remain the originals.

I try to upgrade the Allen Bradley cpu to 1756-L71(RSLogix 5000 v20) but I cannot establish communication with the HMI. The IP addresses of both the the HMI and communication modules have not changed and I am able to ping the HMI address and plc comm card addresses. Is this upgrade not possible or am I missing something? Thanks.