customizer.php error

I am trying to work with the slider on my website, and I get this error message. I just did the latest WordPress update. Any suggestions? Thanks very much!

Fatal error: Call to undefined method WP_Customize_Manager::add_panel() in D:\Hosting\4857213\html\wp-content\themes\sparkling\inc\customizer.php on line 26

Hi @trudi,

Sorry to hear of the problem you are having.

It seems the common unexpected error that occurs due to outdated version of WordPress.

You can try resolving this error as described on the following pages.

Best Regards,