Hi there,
Unfortunately, there is no URL in the secure note to be able to check the case.
It can be caused by several reasons which you need to rule out one by one for your environment. Please kindly follow the steps mentioned in the article below:
https://theme.co/apex/forum/t/popular-questions/204
In addition please make sure that the PHP memory limit is enough to operate the website and the theme. To change the PHP memory limit please kindly read the article below:
https://theme.co/apex/forum/t/troubleshooting-customizer/196 (Not Working or Showing a White Screen section.)
You may need to contact your hosting service provider for some of the steps mentioned above.
Thank you.