This behavior sounds similar to the behavior I encountered here: https://developer.apple.com/forums/thread/737019
Have you tried adding the intermediate certificate (as described in eskimo's post) to the root user's keychain on the EC2 instance? Intermediate WWDR certificates can be downloaded here and would need to be whichever is specified in your development certificate (in my case it was Worldwide Developer Relations - G3)
Topic:
Developer Tools & Services
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Xcode
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