Until you get an answer, try to:
Reset Mask/Object Toolbar
- Tools > Options
- Workspace > Customization > Command Bars
- Click on Mask/Object then click the Reset button
Increase Screen Resolution
Increase Screen Resolution then see if you can reach the toolbar.
Try also to put the Property Bar on that row, where the Mask/Object is hiding, and switch between tools.
Reset the Current Workspace
If you haven't done any customization, simply reset the current workspace (hold down F8 while the application is starting).
Please tell us how things turn out.