Hi @Jadeeleanor! Happy to see you here. Welcome to Community 
Facebook has made some changes to the mobile display of New Experience pages:
Now, the reviews pages are only available in the mobile Facebook app and if you’re trying to open the page from your mobile browser, Facebook will redirect you to a page with an error.
Unfortunately, since this is a Facebook restriction, there’s nothing we can do on the side of the widget at the moment, please accept my apologies for this 
I’d like to tell you that we already have a request to make the button work on mobile on our Wishlist. Please vote for this feature to get a notification upon its release.
Feel free to leave a comment there or any insights you have as it helps us improve our apps 