Not trying to be rude, but this is a clear case for having regular backups and why updates should not be run on a live site without testing.
There are too many variables for us to help troubleshoot errors. It could be that you updated PHP, or your server was updated. Not just the WordPress core, plugins or theme.
You are going to need to pull a copy of this site onto a development platform and test for conflicts while completing the update process.
- Make a backup (or use one if you have been taking regular backups)
- Create a development platform.
- Install the backup.
- Find the conflict / problem by disabling other plugins. (hopefully it’s not the theme).
- Check for compatibility with your server (php, etc)
- If that doesn’t work find a new widget plugin.