Online result validation and result viewing online both require internet connection. This error usually means that you are not connected to the internet or you cannot reach 3dmark.com server at all. 3dmark.com itself is almost certainly still online - you just can't reach it.
In some cases this could be caused by an antivirus or other security software preventing 3DMark from connecting the 3dmark.com online service. This could also occur due to a proxy server that requires authentication. 3DMark does not support configurations where your internet connection requires you to authenticate to a proxy server. Also note that www.3dmark.com uses HTTPS and corporate proxy servers that do "man-in-the-middle" packet inspection that breaks HTTPS can also prevent 3DMark from contacting www.3dmark.com.