Building iOS Native App Client (web builder)

Hi im setting up an on premise version of Appcenter 4.3.1. I have uploaded the code signing cert & when I choose the mobileprovision file it does not give me any error. However when I click Build App Center it gives me an error "Could Not Save - There was a server error, and your app could not be saved"

What could have gone wrong? Installation did not prompt any error.

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