Issue
Patterned line types or non-continuous line types are not displaying properly in model space or layout space.
Cause
Most commonly, this happens because various system variables related to line types need to be adjusted.
Resolution
Start by setting LTSCALE to 1, MSLTSCALE to 1, and PSLTSCALE to 1. Ensure that your drawing scale is set correctly as well. If you are drawing a line 500,000 units long and your drawing scale is set to 1:1, the dashes and gaps will not show up until you zoom in a considerable amount. In most line types, the dashes and gaps are defined in fractions of units at their plotted lengths. After adjusting all system variables above and ensuring viewport and model space annotative scales are set properly, type REGEN and then press enter. This should update the appearance of any patterned line types. (Note that 3D Polylines never display line types other than continuous.)