That WordPress plugin should be able to handle this, but otherwise it's just a line in .htaccess (which will also be more efficient):
RewriteRule ^ shop / / products / [R=302,L]
The previous directive should go after the
RewriteBase directives but before Anything else from WordPress.
/ products /.
302 (temporary) redirect to
301 (permanent) when you are sure it is working well. Temporary redirects are easier to test because the browser does not cache them.