Don't know if you resolved your problem yet, but just to clarify...
If a Powerflex drive displays "Not Enabled", it means that drive has a hardwired issue that will prevent it from running. Most typically, this means that one of the 6 inputs is set as the "Enable" input and that input is currently false.
If a Powerflex drive displays "Stopped", it means that the drive is not running, but there is nothing actively keeping it from running. If the drive receives a brief "Start" command, it will run.
If a Powerflex drive displays "Stopped Asserted", it means that the drive is not running AND MORE IMPORTANTLY that the drive is still receiving a "Stop" command. In the old hardwired days, this would be the equivalent of some one holding in the stop button.
So, if your drive displays "Stopped" and then changes to "Stop Asserted" when you press your start button, it tells me that your start button is somehow causing a "Stop" command to be issued to the drive. I assume that your start button is wired into a PLC and the PLC sends the command signals to the drive??? If the PLC is communicating to the drive over deviceNet and this only changed when you installed the new drive, I would suspect that the DeviceNet mapping was somehow changed.