This normally happens suddenly if your hosting server had some update or or configuration setting or a security setting was changed. We suspect a cookie setting issue on the hosting server or some patch on the hosting server affecting the cookie setting and session setting. We recommend first contacting your hosting provider to fix the server settings.
To set all requests coming in to domain.com get redirected to www.domain.com follow the below instructions. htttp://www. redirects are essential for good SEO of the website.