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Certificate is not trusted by iOS devices but it is trusted by Android and Windows devices

I’ve deployed ASP.NET on IIS servers (Windows Server 2016). I have purchased a standard certificate package and apply to my server as your instruction.

The certificate works with all my devices Windows, Android but when I try to authenticate with an iPhone (iPhone 6s Plus, iPhone 7, iOS 10), it says that the certificate of the server is “Error Domain=NSPOSIXErrorDomain Code=100 "Protocol error"”. 

Please help me to solve this problem.

Thanks alot


Hey @HuyNgo,


When you installed the certificate to your server, did you make sure to include all the certificate files issued to you (including the intermediate certificate). What you're describing sounds like it might be an incomplete chain, which members here on the community would be happy to help check for you if you can share the domain name the SSL installation was for?


CG - GoDaddy | Community Moderator
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Hi @CG,

I had downloaded certificate zip package from GoDaddy (for IIS). I extracted it and got 2 files (*.crt and *iis_intermediates.p7b). Then I installed as your instruction in GoDaddy website. (

My domain name is

Please help me double check if I have a mistake.