If you see this error or similar after using Migration Manager in Vectorworks 2017 to import an old workspace from a previous version: "This command requries a Multicable on modifiable layers to be selected. Click "OK" and pick a Multicable"
This can be remedied simply by removing the command(s) via the Workspace Editor, and re-adding it from the All Menus section of the editor. Steps on using the Workspace Editor can be found here:
Edited by JimW