Try switching to the default WP theme first (eg. Twenty Fifteen) and activate the plugin again.
If the default theme works, then you should contact the Animal Hub theme’s author since there might be something causing that fatal error.
But if it still doesn’t work even with the default theme, so it might be from the other factor. In this case, you can post your question on the plugin’s forum: https://wordpress.org/plugins/contact-form-7/ . Or, try google using the keywords as the plugin name and the error message.
Actually I like white and clean style but honestly the site looks unfinished to me somehow (I thought the CSS wasn’t loaded at first). And I think that the overall design of the site is scattered. It looks like the elements don’t match with each other (like the body and header). Maybe because they hadn’t been initially designed together in the first place? They might need some refinement in my opinion.
But it’s good to see the changes and movement. Keep it up!
November is a great month for me but as FinalDestiny said, the sales dropped in 4-5 days lately.