You can try to reset your user files.
- Open Copy User Settings from the Utilities menu
- Choose the option to Reset to a clean set
- Click OK
- Choose Yes and then OK on the next two dialogs
This will restore Toad to a clean state as if it were freshly installed. Your existing user files will be backed up to %APPDATA%\Dell\Toad for Oracle\12.6_bak.
Now, start Toad, make connection, and try Code Insight again. If it works you can close Toad and copy any configuration files over from the backed up set to the new (%APPDATA%\Dell\Toad for Oracle\12.6) . I'd recommend copying only what is absolutely necessary. For example...
- CONNECTION*.INI (all of your saved connections)
- SavedSQL.dat (SQL Recall)
- ToadActions.dat (Automation Designer apps and actions)
- Workspaces.dat (saved Workspaces)
- *.tpr (Project Manager projects)
If resetting your user files does not work I'd try downloading the latest Toad trial and seeing if it works.