Hi all,
No wider known issues at the time of this thread, though it sounds like most were able to get back on already by now.
If anyone is still having issues, first make sure you’re not accidentally trying to connect to a different version that may not be online (such as the PTR). Otherwise restarting the Battle.net app/your computer would sort out most common problems.
For any persistent errors after that, you can find more info and troubleshooting steps over on this page: