Why can't I communicate to the SLC Scanner module?

Why can't I communicate from the HI 2110WI, HI 2151/20WC, HI 2151/30WC or the HI 2160RC, to the SLC Scanner module when I have more than 16 devices configured?

The HI 2110WI, HI 2151/20WC, HI 2151/30WC and the HI 2160RC units are a 1/4 rack device on the RIO connection. The SLC Scanner module only has 4 racks available, so can handle four, 1/4 rack devices per rack for a total of sixteen 1/4 rack devices. If you have more than 16 quarter rack devices on the same scanner module, then you have utilized all the available I/O for the scanner.