Image Sizes: Image sizes must be prefixed with theme slug. Check functions.php line 51
Scripts/Styles Handle
Styles/scripts handle should be prefixed using theme slug. E.g: line 361 in functions.php becomes
wp_enqueue_style( 'sitepoint-base-theme-style', get_stylesheet_uri() );
Exception to this rule is third party scripts/styles
Check for all scripts/styles as it is missing in almost all custom styles/scripts
functions.php
line 51wp_enqueue_style( 'sitepoint-base-theme-style', get_stylesheet_uri() );