My guess is that the problem is because of what you are asking about here:
Could you try using the default WordPress .htaccess configuration and see if you are still getting an error?
Instead I just reverted back to a wordpress backup from 2 days ago (with the original htaccess file). Although, the problem was still there. But when I cleared all my cache. cookies and history, it started to work again.
Kind of a weird situation but im glad I sorted it out.
Do you think the wp optimize plugin could have anything to do with this?
I don’t know. If you can figure that out, and why that is the case, please let us know. We can’t get into a lot of WordPress development on this forum, but it’s good to know about conflicts between the WP Discourse plugin and any other WordPress plugins. It makes debugging issues a lot easier.
对于遇到此错误的其他人，我通过为客户端域名填写 sso provider secrets 设置解决了该问题：
在 Discourse 代码中，如果未设置此密钥，调用 OpenSSL::HMAC.hexdigest 时会在日志中报出以下错误：
TypeError (no implicit conversion of nil into String) /var/www/discourse/lib/single_sign_on.rb:114:in `hexdigest’
以下是相关的代码路径：
此错误消息确实应该得到改进！_编辑：已经改进——参见 https://meta.discourse.org/t/confusing-unpolished-error-message-when-using-discourse-as-sso-provider/123762_
