A problem with functions.php file on my WordPress site

by

You need to enable your debug log to know actual problem on your site.

Enable Debug log from your site though below steps:

  1. Open wp-config.php from your WordPress setup.

  2. Add below lines

    define( ‘WP_DEBUG’, true );

    define( ‘WP_DEBUG_LOG’, true );

    define( ‘WP_DEBUG_DISPLAY’, true );

And just refresh the page.

Now you can see the error message’s and warnings behind your problem.

For more information @see https://codex.wordpress.org/Debugging_in_WordPress

So, You know the actual reason of why functions.php not working on your site.