Problem using formatter

Using nano 6.3 on Debian bullseye.

I am trying to use pandoc to tidy up and reformat markdown files. So, I
have the following two lines at the top of my markdown.nanorc file:

syntax "Markdown" "\.(md|mkd|mkdn|markdown)$"
formatter pandoc --wrap=none -t
markdown-simple_tables-pipe_tables-multiline_tables

When I hit M-F, the screen flashes, but the content of the buffer is not
changed. However, when I quit nano, the properly formatted buffer is
visible in the terminal.

Attached is a sample file, and what my terminal looks like after I quit
nano.

Robert.

-- 
Robert Goulding
Director, John J. Reilly Center for Science, Technology, and Values;
Director, Program in History and Philosophy of Science;
Assoc. Professor, Program of Liberal Studies,
Fellow, Medieval Institute,
University of Notre Dame.