The error details should be shown in Diagnostic Viewer. Is the error related to block input/output size, dimenstion or non-scalar? If so, can you inspect the data defined in the Test Assessment block ("Int1" and "SigGen"). The size of both "Int1" and "SigGen" should be 1 instead of 2, since Demux is used. Can you change the size of the data defined to 1 and try again?