Flushing your DNS cache is a good opening gambit when you're trying to troubleshoot network connection issues on Ubuntu.
https://www.howtogeek.com/how-to-flush-dns-cache-in-ubuntu/?utm_source=dlvr.it&utm_medium=blogger
https://www.howtogeek.com/how-to-flush-dns-cache-in-ubuntu/?utm_source=dlvr.it&utm_medium=blogger