Suddenly Discogs is working for me again. I don't know if it's something they changed at their end, or because I tried something with my browsers. This may be totally irrelevant, but I tried visiting in Chrome, where it didn't work, and Firefox, where it did, and then (temporarily) changed my default browser to the latter. Thought it was worth mentioning in case it triggered Windows to allow the connection to Discogs. But I have no idea how these things work, so it may have nothing to do with it.