Build 1.75.2.18 on Win10. I open new torrents from magnet links, they stay listed as magnet:… and soon get a red X next to them. They stayed like that overnight, this morning I rebooted Windows and they began to work, but it happened again a few hours later. Rebooted a second time and they are still stuck.
I added a new one just now, same thing. So I thought I'd try the torrent instead of the magnet link as I hadn't closed the download page yet. It told me I already had that task, so I deleted it, opened the torrent file, and it's working. So it may be that the problem is only with torrents.