Permalinks is a feature within WordPress that allows us to setup the desired choice of URL structure. However, changes in permalinks can create errors in loading the page.
Solution
Make sure you check if .htaccess file is already available in the folder where you installed WordPress. If .htacces is not found, then createblank .htacess. Make sure that your hostinggives CHMOD 666 permission. Go to the Settings in the WordPress dashboard and change your permalinks structure to default option, save the changes, again change the permalink option to custom mode and save again.