As quoted from the linked post.
It looks like you’re part of one of our experiments. The logged-in mobile web experience is currently unavailable for a portion of users. To access the site you can log on via desktop, the mobile apps, or wait for the experiment to conclude.
This is separate from the API issue. This will actually BLOCK you from even viewing reddit on your phone without using the official app.
Archive.org link in case the post is removed.
I think social media is a dead stick. I can’t put in words what’s next, but it’s both scarier and more amazing. Whatever it is. But we are basically in 2006/2007 all over again, where everything we are used to is being snatched away from us.