Users getting errors reading the printed targets should perform a printer head cleaning to make sure that the nozzles are clean and in proper working order. Once that is complete reprint the targets and make sure that the patches appear clear so that there is no banding going in them.
When the ColorMunki hardware is trying to read through a test chart, it is expecting to see the white of the paper and then each patch sized correctly then ending on the white of the paper. Trying to scale down the chart will effect this greatly and almost always result in failures where the chart is unreadable. In order to read the chart without errors the charts must be printed directly through the print driver with color management shut off to 8 1/2 by 11 inch size media.
If you are printing the chart to size correctly and the patches are clear of all banding, but you are still getting errors where the marquee will not move forward to the next row, review the image on the screen and see if the colors match what you are trying to read in your printed test chart. If these patches are a different color or appear completely off perhaps there may have been color management turned on somewhere and the software is expecting a certain set of values but the device is giving another based on these measurements.
The last thing that you may want to check is that the driver of the printer is up to date. If the print driver is not current you will also get failures.