GDL Explorer requires a "Master.gdl" file to work. If you do not have one present in your Library you could copy the one from the example Library provided in the samples. The "Master. gdl" stores material, linetype, etc. defaults for all objects in your loaded library.
David Larrew, AIA, GDLA, GSRC
Architectural Technology Specialist
a r c h i S O L U T I O N S
WIN7-10/ OSX 10.15.7
AC 5.1-25 USA