When one attempts to copy members or surfaces from inside the Physical Modeling mode, without selecting the corresponding nodes along with it, an error is generated as shown next
Steps to Reproduce
Open any STAAD.Pro model in the physical modeling mode.
Select a beam or a surface without selecting the associated nodes.
Try to copy the entity.
The copy fails and "Sequence contains no elements" message appears in the Message Log
Note : The error only affects copy operation in the Physical Modeling mode
Select the nodes along with the entities and the copy should work fine.
The problem will be addressed in the STAAD.Pro Connect Edition Update 3.