Because I keep coming back to this question, I will leave my answer here for the solution that works for me. It turns out that for a same public/private key developer identifier of me, it's installed twice in my keychain. Both have private key. But when I compare, one is private key of me within my developer organisation, and another one is private key of me as a personal developer. It turns out Xcode keeps trying using the wrong key. Removing the wrong duplicate key solves all the problem. Hey future me, check this one first next time!

For Xcode 13 (maybe earlier?) - The key to this is to use the "Build Settings" tab, not the "Signing and Capabilities" tab in your Target Settings. Once you are in "Build Settings", search for the "Signing" section (you can type "Signing" in the search box). There you will see a sub-section called Code Signing Identity. In that section you can click on each line and directly choose any certificate you have in your keychain. You need to do that for all of the relevant configurations (the ones that you want to upload to TestFlight/AppStore). When you go back to the "Signing and Capabilities" tab, you should see the results of what you did and the error should have gone away.

我从下面的答案中得到了灵感:https://stackoverflow.com/a/37043501/826946

但我认为明确地列出这一点可能会有所帮助。

“这是苹果门户网站的一个漏洞。他们在配置配置文件中缺少一个必要的字段。他们在2009年6月16日晚些时候修复了这个错误。”

对我来说，只有当证书和两个密钥都在Login keychain中时，它才有效。我之前创建了一个开发钥匙链，但是Xcode管理器在那里找不到钥匙。所以我把它们移回登录，退出钥匙链工具-瞧，Xcode管理器中的错误消失了!这是在3.1.3 SDK的雪豹10.6.2上。

这里的每个人都错了。你所需要做的就是按照苹果在“管理你的数字身份”中提供的步骤操作。

它指导你通过Xcode导出你的证书，并通过Xcode重新导入。它工作得很好，但要确保你的用户名在两台电脑上是相同的，否则就会失败。

我花了几个小时处理这个fershluggage问题，它是在更新开发许可证后突然出现的。重申一下，一切都很顺利，然后(感谢苹果!)一切都搞砸了，一直搞砸下去。苹果官方的故障排除步骤(上面有链接)或这里提到的可能的解决步骤都没有为我解决这个问题。

最后，我删除了我的开发证书和发布证书，在配置门户中撤销它们，然后让Xcode自动刷新/发布它们。在任何顺序中，没有其他方法能够将所需的证书和私钥正确地连接到我的密钥链中。