Split: Blank Screen on Customizer

I have purchased and installed High End theme to wordpress as well. I have the same issue…… “But in the WordPress dashboard – when I got to Appearance/Customize, the Preview Page is blank. The directory does appear on the left side of the screen, but the rest of the page is blank? I’ve tried several of the recommended solutions, but still nothing. Thanks in advance for any help.”…… I have tried increasing my max_execution_time and WP_MEMORY_LIMIT, but that did not help, in fact after I did that it gave me error 500 everytime I clicked on customize. Please help. Thank you