[Cause]
An element cannot be added to the system I/O scan. When this error occurs, ControlNet I/O cannot operate. Possible causes are:
* Scanner list configuration is invalid.
* Too many I/O points for a CNET device.
* Too many I/O points in the entire system.
[Countermeasure]
Check that all I/O is valid. Check every CNET device and verify that its size is appropriate. The maximum I/O count is limited by the system maximum I/O count.