So if your Lay Theme Website was heavily customized with custom code, chances are your customizations won't work with the new Lay Theme versions 3.0.0 and later.
You could rewrite your customizations (CSS and JS) to work with the altered new HTML of Lay Theme. (No tutorials here, you'd need to know the basics of how to view HTML code of a website and write CSS and JS for it.)
But you could also just use the old Lay Theme and old Plugin versions if you like.
However, if your problem has nothing to do with custom code compatibility, but you have a different issue, please just let me know your issue/bug here in the forum and I'll fix it.
If you wish to use the old Lay Theme version, send an email to firstname.lastname@example.org , include your license key and let me know if you had a Lightbox, Carousel or Fullscreen Slider addon in case your license is a Single License.
I'll send the old files to you. It is important that you use the old Lay Theme versions and old Addon versions. The new addon versions are only compatible with the new Lay Theme Versions.
How to install old files:
In "Plugins" you need to delete the Lay Theme Addons. Now upload the old Addons as described in http://laytheme.com/installation.html Step 3
To install the old lay theme, go to Appearance -> Themes. Switch to a different theme. Now click on the Lay Theme Theme and click Delete. Now upload the old lay theme file to install the old Lay Theme as described in http://laytheme.com/installation.html Step 3
I believe using the new version of Lay Theme and new Plugin Versions is better because your website would load faster. However, using the old files is the way to go if you're happy with how your website was and you're not looking to change your custom code.