Can't Sign in

I can Sign in in client, but not for Earning rewards for watching, or for Support. The moment I press Sign in I am automatically Signed out and redirected to the previous page. I sent a Bug report via client button, and also got a message for some error, but somehow from Bug report page I can write here and it says I'm Signed in. I tried again for Watch rewards and Support, it's still not working. What's going on? Screenshots:

We're testing a new feature that gives the option to view discussion comments in chronological order. Some testers have pointed out situations in which they feel a linear view could be helpful, so we'd like see how you guys make use of it.

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