#10 Error: Object reference not set to an instance of an object.

[Richard Winks]

I am running Windows 10.0.14393.
Just downloaded and installed PdfMerge version 1.22.4694.38966.

First attempt to merge 2 files, I get the following error message:

Object reference not set to an instance of an object.
On Line:
C:...\Contract Marked Paid in Full 17410.pdf;all;include

The indicated file name is the first of 2 files. The error message does not help me determine the cause of the problem, ie. whether it is a program bug or something I have done.