I am having the same issues except that I am starting with a whole new install. WordPress 5.0 and only have Elementor and Popbox for Elementor installed. The theme is twenty nineteen.
When you click on the download voucher button the popbox opens and when you enter the name and email it gives a server error.
I used mail check and that works okay and have contacted Bluehost and everything is working on their end they said to contact wordpress support.
The site is clinicalnutritiondoctor.com
