The most common cause is a Javascript conflict.
- Begin by deactivating all plugins other than WooCommerce, if used. If the menus now work, one of your plugins is conflicting
- Activate each plugin one at a time, reloading your homepage in between to test the menus. When you find the problem, ensure the plugin has been updated, is actively maintained (last update is less than 6 months or within 30 days of a WordPress update) or replace it with a similar plugin.
- If plugins did not solve the problem, check your posts and widgets for any Javascript or HTML you may have inserted and remove it.
- For posts, Javascript should not be inserted into the Text tab.
- For text widgets, only web-ready widget code should ever be inserted. Full scripts or plugin javascript must be added to template files and not text widgets.