When testing a scan using the provided ssecls command-line demonstration tool, the documentation states that a file or folder can be selected to be scanned. If you provide a directory for scanning to the command-line scanner provided with SPE 9.1, you will get an error.
There is a defect in the command-line scanner provided with Protection Engine 9.1.
This will be fixed in the command-line scanner ssecls binary and Java examples with the SPE 9.2 release.
Till then, the command-line scanner which is part of previous SPE releases prior to v9.1 can be used. There is no functional difference/loss in previous command line scanner version compared to 9.1.