Go to Score Manager, click on the piano line, click on Abbreviated Staff Name, and delete it.

If the Piano is notated as a 2-staff {Staff Group} instrument, then the Abbreviated Name is a Group Name rather than a Staff Name.

I've gone to Staff Attributes and clicked on staff name and staff abbreviation to remove and I'm not successful....can you help?

Do what Mike Rosen said.

I tried this and it didn't work.

Mike, try deleting the name, and replacing it with a space. Just tap the spacebar once. I seem to recall having to do that, in the past.

If you can’t make it work, send me the Finale file at wawoodman at aol dot com.