Subject says it all but here are some words.
Had that problem yesterday and this morning, but it’s since been fixed.
You might have to wait it out.
I had that problem when using my bookmark. I had to go through the main TR website and rebookmark the site.
Sorry about that! There was an issue with the configuration with/at Discourse (who hosts the Forum). They handle that redirect for athletes may have forum.trainerroad.com bookmarked, but not everyone was being consistently redirected to TrainerRoad - Cycling & Training Forum. We got in touch with them and it seems to be working now!