I/O COMM ERR (7000) AT ACS800 DRIVE WITH RMIO-11C BOARD AND ENCODER MODULE ONLY.
the ERR 7000 mean error communication between the control board and the module.
Check thoroughly the optic fiber and the connection, and verify do not have floating ground reference in your system.
You need furthermore to check if the new drive have one most recent FW version than the old.
In this case it is possible, but not sure, that the different version of the FW may cause the reported error.
If you not have confidence with the update procedure of the drive, I'll suggest you to contact ABB service in your area
Hope this help you