No Internet Connection on installation

I just flashed Dietpi onto an microSD card and put it in my raspberry pi. It keeps giving me the error message of no internet connection without any time delay. When entering the config and running the internet test there on the same URL( It says I am online. I am using ethernet and can run the update through the dietpi-software however am still unable to install any software due to the error message appearing immediately.

 [Info] Testing connection to
 [Info] Max duration of 20 seconds, please wait...
 [Failed] Connection test | An issue has occured

and running sudo apt-get update gets this

Fetched 180 kB in 1min 32s (1,948 B/s)
Reading package lists... Done
W: The repository ' stretch Release' does not have a Release file.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: Failed to fetch  server certificate verification failed. CAfile: /etc/ssl/certs/ca-certificates.crt CRLfile: none
E: Some index files failed to download. They have been ignored, or old ones used instead.