我也遇到了同样的问题:我第一次是在跑步时把证书下载到我的小MacBook上的。当我试图在iMac上安装证书时…然后我遇到了这一页上描述的问题。

和你们很多人一样，我花了几个小时把头发揪出来，然后我按照下面的步骤来解决它:

Close all your stuff except your webpage that should be logged into App Dev center. Open Xcode. Click WINDOW > ORGANIZER. Then click the Devices tab and select "Provisioning Profiles" on the left. That should bring up your provisioning profiles. Highlight one by one (if more than 1), right click and delete profile. Yes, just do it! Delete them all! (I kept making a new one after a new one trying to make the thing work.) From the first page you see after logging into the App Dev Center on the right side click "iOS PROVISIONING PORTAL" > (do not "launch assistant"). Instead click on the left side. Select CERTIFICATES. You will probably have just one line listed with your name/company - from there click on the right side REVOKE. Click OK to verify that's what you want to do. On the same page click DEVICES. Click the box next to your device you are trying to provision and click REMOVE SELECTED. Again click OK to verify. Wait about 2 minutes to let Apple do their thing. Now click on "HOME" that is on the left side navigation. Click "Launch Assistant" create a new app ID - call it whatever you want. Just make sure it's unique enough to know that's the one you just created because the others you've been messing with all day will not be deleted from Apples Dev Center. You should be able to follow the rest of the Assistant without troubles -- the main thing is you just had to delete your old provision profiles and start over.

好运！

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。

我得到的最佳答案是导出您的密钥，而不是仅仅试图导入证书文件。

当您从生成请求的密钥链中导出密钥时，您将得到一个Certificates。P12文件，将需要的键滚动在一起。

然后将其导入新计算机。

对于这样的密钥，最好保留一个滚动的证书包文件，因为很多时候“公共”密钥或证书文件不足以进行恢复。

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。

我解出来了。 我不得不把。cer文件拖到KeyChain Access中。但请确保左上角的“Login”已被选中。否则，Xcode将无法看到证书，也就无法为你的代码签名。

苹果在这方面还有改进的空间....

我也遇到了同样的问题，试过了所有方法。不管出于什么原因，解决方案是我所有的证书都迁移到一个名为“microsoft_intermediate_certificates”的密钥链上。因为它可能发生在Xcode升级期间，我完全不知道为什么，但它可能会帮助到一些人。

我将微软钥匙串的所有内容移动到登录钥匙串，一切恢复正常。