The possible causes are:

1. When trying to enter into a program or execute an empty block or containing the label (block number).
2. In the "Pattern repeat canned cycle (G66)", "Roughing canned cycle along the X axis (G68)" or "Roughing canned cycle along the Z axis (G69)" when parameter "S" (beginning of profile) is greater than parameter "E" (end of profile).

The solution for each cause is:

1. The CNC cannot enter into the program or execute an empty line. To enter an empty line in the program, use the «;» symbol at the beginning of that block. The CNC will ignore the rest of the block.
2. The value of parameter "S" (block where the profile definition begins) must be lower than the value of parameter "E" (block where the profile definition ends).