Block cannot be exploded in AutoCAD | AutoCAD 2018 ...
When you tried to explode a block, you received the following message on the command line: 1 could not be exploded. The geometry remains a block. Beginning with AutoCAD® 2006, the Allow Exploding option was added to the Block Definition dialog box. If this option is not selected when a block is created, instances of this block cannot be exploded.