Hi Issac,
Thanks for reaching out and thank you for using BoldGrid Post and Page Builder for WordPress!
We inspected your site and noticed that you’re using what appears to be a child theme of the BoldGrid Legacy theme Hydra.
I’m pretty sure you can bring it to compatibility but you would need to access your theme code directly to resolve it. You would need to locate the PHP Fatal error and resolve the Undefined constant which should be somewhere in your /templates/header file.
It would help if you’re still in contact with the developer of the child-theme. You may be able to recreate it using a more up to date Post and Page Builder compatible theme such as Crio Pro WordPress theme.
I know this isn’t much but I hope it helps in some way Issac. Please let us know if you have any other questions for us.