It seems that you’re using an old version of the theme. Can you try to use the latest version of the theme. Also it seems I’ve seen that all the required plugins are installed & your site is running perfectly. I can’t see any fatal error while it’s activated right now. We’ve 2.6 version running for teriz theme you can check the changelog from there: https://docs.themeregion.com/teriz/#changelog
Try to get the latest version which will reduce such fatal error issues as we’ve updated the theme along with core plugins to match with the latest version of PHP. Hopefully updating will resolve the issues.