The customer was trying to generate a Datamatrix barcode that would fit in a small area on the label. During label development he started with Symbol Size Auto. The Datamatrix barcode was printing too large. He then tried using the fixed Datamatrix symbol sizes. At this point the Datamatrix barcode stopped printing on the label.
Solution 1) Change the Symbol size back to Auto and reduce the cell size of the Datamatrix barcode to suit your size requirements.
Solution 2) Change the Symbol size large enough to handle the data and reduce the cell size of the Datamatrix barcode to suit your size requirements.
The following are sample labels used to reflect the customer's issue.