If MicroStation ®V8i is installed after installing SIGMA, the toolbar will come up blank (i.e. no icons). Problem can be remedied by copying SIGMA.dll, which can be found in SIGMA folder, to the C:\Program Files\Bentley\MicroStation\mdlapps\icons folder. This is assuming that your MicroStation is installed in default location. If you have MicroStation® installed elsewhere, please adjust the above path accordingly (i.e. locate the mdlapps folder and if the folder named icons is not already in there, create a new icons folder and paste our dll within that icons folder).
Please note that for MicroStation® V8i (Select Series 2), you should copy GuidSIGN.dll file into: C:\Program Files\Bentley\MicroStation® V8i (SELECTseries)\MicroStation\icons Or if you have 64-bit version of Windows, please copy the GuidSIGN.dll to: C:\Program Files (x86)\Bentley\MicroStation® V8i (SELECTseries)\MicroStation\icons