Can’t add elements to loop template

I’ve used your plugin with great success on other sites, but on this latest site when I try to create a new loop template, it won’t allow me to add elements. I see the header, and the footer, but it won’t allow me to add any elements to the workspace to create the loop. Any ideas? This is a brand new install with Elementor Pro and WooCommerce (Woo is not configured yet, but is installed).