When experiencing an issue when customising your store, it can often be related to an error coming from some custom javascript that has been applied. The best way to review those errors is through the browsers console, which each modern browser uses to display client-side errors or warnings that may have occurred.
Each browser has a slightly different way of accessing their console, so you can use the following page to enable it for your browser.
Chrome
To open the console in Chrome, you can use the keyboard shortcut Command+Option+J (Mac) or Control+Shift+J (Windows, Linux, Chrome OS).
Alternatively, you can use the Chrome menu in the top right hand corner of the browser, and select "More Tools" and then "Developer Tools". You may need to select the Console tab in the developer tools that then displays.
Edge
To open the console in Edge, you can use the keyboard shortcut Command+Option+J (Mac) or Control+Shift+J (Windows, Linux).
Alternatively, you can use the Edge menu in the top right hand corner of the browser, and select "More Tools" and then "Developer Tools". You may need to select the Console tab in the developer tools that then displays.
Firefox
To open the console in Firefox, you can use the keyboard shortcut Command+Option+K (Mac) or Control+Shift+K (Windows, Linux)
It can also be opened from the Firefox menu, choose "Web Console" from the "Web Developer" submenu.
Safari
To open the console in Safari, you first need to enable their Develop tools. You can do that from "Preferences", as found under the "Safari" menu in the Mac menu bar. Within the "Advanced" section of the preferences, check the option labelled "Show Develop menu in the menu bar".
Once enabled, you can then open the console with the keyboard shortcut Command+Option+C, or by selecting "Show JavaScript Console" in the "Develop" menu of the Mac menu bar.