Getting Error Message for Mobile Site

I have the wordapp plugin installed on my woocommerce site. The mobile site was working fine for a while but it is now not functioning. When on a mobile device it isn’t showing the Wordapp mobile site at all. Not sure what is wrong. When I go to the wordapp site to build the app there is an error message that says Cannot Modify Header Information. Obviously, I am an amateur and have no idea what I am doing but would really appreciate any help in getting this resolved. Thanks so much.

https://wordpress.org/plugins/wordapp-mobile-app/