When a theme update becomes available, you’ll also see a notification on the Appearance » Themes page.
Updates are really important for the security and performance of your WordPress website. Aside from security and bug fixes, theme developers can also introduce new features with these updates.
You can fix the issue yourself. Probably, the updated theme is conflicting with the previous Guto toolkit plugin. Try deleting the old Guto Toolkit plugin before activating the updated theme. Then install the updated Guto Toolkit plugin from Appearance > Install Plugins.
