Portfolio pages getting 404 error

I’m having some issues with the portfolio section of Savia. I can add new portfolio items, but they don’t show up in the portfolio admin section. I only get this message showing.

Fatal error: Call to undefined function ct_first_image_tn() in /home/content/p3pnexwpnas04_data02/01/2941001/html/wp-content/plugins/ct-custom-posts/ct-custom-posts.php on line 70

The images show up in the portfolio carousel on the main page, but when clicked on it takes me to a 404 error.

Can you give me some suggestions to fix this?

Thanks in advance.