You open a Visio or AutoCAD file in SI 2018 and none of the "SI 2018" stuff loads, e.g. no Project Editor or D-Tools SI 2018 Shapes window open.
This is likely due to Visio or AutoCAD having been installed after the SI 2018 Client was installed, so our Add-Ins for these could not be loaded.
To fix, open SI 2018 and then got to Start->Setup->Control Panel:
Under the Drawing Add-Ins Manager section, run the appropriate function for your Visio, either 32-bit or 64-bit. In most cases, Visio will be installed as 32-bit.
When you run this file it will open the following interface:
You will get a confirmation message: