You may face an issue where you access your site center to edit sites and you notice that it's not displayed properly. Also, the buttons to switch from pages, News, Locker, and tools don't work, and some other functions are messed up as well as seen in the screenshot below.
The issue may be related to your browser loading a broken version of the page. To solve it, kindly clear your cache by following the steps indicated in this article on How-to-clear-your-browser-cache. Also, consider testing it with a different browser, such as Google Chrome if you're not.
If this issue keeps occurring after you clear your cache, please open a support ticket and our agents will investigate the issue. Provide a screenshot of how your Site Center appears or a reproduction video of the issue and the name of the browser you’re using.