fatal error

I nstall Scribe and when I activated it from my dashboard this is what error I got Fatal error: Class 'Upfront_Permissions' not found in /home/content/p3pnexwpnas02_data03/62/2469862/html/wp-content/themes/upfront/library/servers/class_upfront_layout_revisions.php on line 25

It will not allow me back to my old theme.