DNS Error on Multisite

Hello... I have carefully followed all instructions to set up my multisite but keep getting the following DNS error;

"This site can’t be reached

test1.onlinewebs.biz’s server DNS address could not be found.:

The primary site is accessible. I updated the config file and htaccess as instructed. I changed name servers over 20 hours ago.

Any advice most welcome.

Regards

Larry