3D Tools are not available in Tasks, e.g. Solids Modeling, Surface Modeling or Feature Modeling tools.
Please check if the dgn file currently open is a 3D file since these tools are not available in 2D files.
Solid Modeling Toolbox not showing up in the taskbar: http://communities.bentley.com/products/microstation/f/273/p/100865/299194#299194
Where is the Modeling workflow? https://communities.bentley.com/products/microstation/w/microstation__wiki/24985/where-is-the-modeling-workflow
How to easily find any tool in MicroStation CONNECT Edition: https://communities.bentley.com/products/microstation/w/microstation__wiki/27894/how-to-easily-find-any-tool-in-microstation-connect-edition