On Thursday this week, I updated Opera, which I use as my main web browser. Installation seemed to go smoothly but, after restarting it, I found I couldn’t visit any web pages, instead hitting an ERR_ADDRESS_UNREACHABLE message. I switched to Firefox, which was working fine, but my search-fu seemed to desert me and so I left it for the day.
Fortunately, I had a brainwave yesterday morning. I looked at Little Snitch, a piece of firewall software for macOS that I installed when I was studying digital forensics with the Open University and realised it was the source of the block, because I have to install Opera manually rather than from the App store and so it was flagged as an app from an unverified developer. I’m willing to trust them, so I removed the blocking rule and all was back to operation.
It is probably a fairly rare combination of factors, noted here for my future reference!