404 error in multsite

Hi Mate:

I installed the required plugins and themes from WPMUDEV but unfortunately after creating a new post and after publishing and view post shows a message as given below:

The requested URL /2017/03/27/sydney-emergency-plumbers-eba-fundamentals-explained/ was not found on this server.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.

all help needed.