Slider settings not loading after domain move

Our new website is almost done and we moved it from the test server to the live one.
I restored the full SQL backup and the slides show up like normal.
But I can edit nor add one.

As soon as I try the slides page load, but no options will show or are empty.
No backgrounds and no slider preview.

I can change the background, but the update will not show on the slider page. (thumbnail)

Hope you can help.

BTW: the plugin was included in a theme I got from themeforest.

https://wordpress.org/plugins/master-slider/