Activate Reference option greyed out.Sometimes it is not possible to activate a reference. Why is that?
Open in other session, display mode True Hidden Line etc.From the MicroStation Help Documentation,
The reference cannot be activated if:- The display of the reference is turned off.- It is open for editing in another session.- It is a perspective reference attachment.- The reference display style is set to True Hidden Line.- The reference orientation is Geographic Reprojected. However, the reference orientation Geographic AEC Transform can be activated.- The master file is read only and the reference is to another model in the master file.- The file format is anything other than V8 DGN, DWG, or DXF.When a reference is activated:- Only operations on the activated reference are permitted.- By default, all elements in references above the activated reference in the file hierarchy, as well as the active model, are displayed with an override color. You can control whether or not an override color is used, and what the color is, with the Active Reference Override Color preference (Workspace > Preferences > Reference > Active Reference Override Color).- If you activate another reference, the currently activated reference is automatically deactivated.- The reference is locked so that it cannot be edited in another session.- DGN library data, such as levels and level filters, is not available in an activated reference file.