14.4. Fixing invisible tab contents in setting pages

This issue is probably caused by another plugin/theme you use. Some of the plugins/themes do not write their CSS/JS codes in a way that the codes are only applied to pages of their plugin/theme. If this is the case, you can find that plugin/theme by deactivating your plugins/themes one by one and checking the site settings page after each deactivation. After you see that the pages are shown, the last item you deactivated was the problem. If you could, please ask the developer of the item to fix the issue. The plugins/themes should not modify pages of other plugins/themes.