There will be instances when you will import an object, supplied by a client, that comes into CorelDRAW as a lens or with a transparency applied and the Interactive Transparency tool will not allow you to modify it. 
To remove the transparency follow these steps.

1. Open the Lens Docker.  Windows > Dockers > Effects > Lens.
2. Select the object with the transparency.
3. Make sure No Lens Effect is selected in the drop down menu.
4. Click Apply - The lens or transparency object should now be removed. 

Removing Lenses and Transparencies with the Lens Docker works on both vector and raster objects. 

Tip provided by Richard Reilly, Graphic Designer and CorelDRAW Master.