Ensure that the PrivacyPass extension is able to get passes (if installed)
On TBB 9.0.5, "standard" security, using PrivacyPass 2.0.4, on Ubuntu 18.04 when I try to get passes I get a long sequence of Captcha's to solve. Eventually it stops serving Captcha's and I get a green check mark as if I had passed, but the extension still shows no passes acquired.
In Firefox on the same machine, using Tor naively through a socks proxy, Privacy Pass WAI. This seems to support that the issue is specific to TBB rather than PrivacyPass / Cloudflare's treatment of Tor traffic itself.
See also the PrivacyPass bug https://github.com/privacypass/challenge-bypass-extension/issues/99 for this issue. Also possibly-related bug that PrivacyPass doesn't work when the browser spoofs the user-agent string: https://github.com/privacypass/challenge-bypass-extension/issues/106