This would be possibly caused by an improper/incomplete install of the theme. The theme is trying to use files that are not there.
Try the “clean start” method of updating.
1. Switch to a different theme.
2. Delete the current Weaver II Pro theme from the WP theme admin panel.
3. Reinstall Weaver II Pro via the WP theme upload theme install panel.
4. Reactivate Weaver II Pro.
At this point, it should work. If it doesn’t then there are other serious issues with your site – file permissions, perphaps, and you might have to contact the host.
Since you were getting strange plugin errors (which look like corrupted plugin files, or missing plugin files, it is possible your entire site has been hacked, and files replaced or missing.