Thank you for writing in, most commonly (but not limited) that issue is caused by a broke HTML markup or a CSS syntax error somewhere on your Theme Options, Page > CSS, or Element CSS.
Please check all your custom HTML markup and make sure all tags are written correctly and properly closed.
For the custom CSS, please check all those mentioned custom CSS areas above and check your CSS for syntax error and address it, you can use this tool for checking CSS.
Also, please make sure that your Wordpress version is updated to date 5.2.4 and CLEAR all your caching plugins/features (if any).
If the issue persists, please provide us login credentials in a secure note so we can take a closer look.
Let us know how it goes,