When I select the Sharpen More Command I get this error message: "could not complete the Sharpen More Command" because the selected area is empty. How do you select the area?
Do you have a blank layer targeted rather than one that has pixel content?
Why use the sharpen more command when unsharp mask offers more control?
I concur with Stephen - a blank layer will cause that specific error message.
Ensure that you have the correct layer active/targeted and all should be good.
Dianne, I doubt that any experienced Photoshop users ever use Sharpen More.
The OP may not be an experienced user.
Here is a good resource to get you started on using Sharpen including Unsharp Mask.
If you have further questions, hit us up!
Please confirm that you are not on an empty layer. Posting a screen capture of your Layer panels would be beneficial.