If your connection to the network involves a router, you can try to power cycle the router. If using a wired connection, sometimes un-plugging/re-plugging the ethernet cable is the fix.
I found this thread when the network connection really failed, perhaps it can help, but I'm not sure.
You can also take a look at this thread to get some ideas. Unfortunately there is not mentioned, if it solved the issue.
@arichardhead Have you found a solution for this problem?
In this ask ubuntu thread is written that a VPN caused the problem: