Cannot access Solver

I checked and the workbook prior to attaching it did have the Visual Basic -> Tools -> Reference -> Solver box checked. For some reason the process of uploading it caused the check to be removed. Any reason for this?

My simple model sets Cell O2 to minimum by changing cell J2. It works on another workbook, but only on the top sheet.

I am attaching a new workbook, this time containing the code supplied by Peltier. It doesn't appear to help, and the Solver check mark has been removed.

Thanks to everyone who helped.