"there has been a critical error on your website"

Hello!
I just purchased the Unicon theme, and upon installing the file and activating the theme, this is what I see when I load the site:
https://imgur.com/wegSaUH

I waited until it said that the installation was successful before installing. The site is bealliance.org, I put my old theme back on in the meantime.
Do you know what I can do to get this to work?
Thanks so much for any guidance!
Kerry

Ticket