Ionic iOS Package Build Failing: SecKeychainItemImport: Unknown format in import

I’m trying to use the CLI command
ionic package build ios --package package_name

The build fails with the following information:
image

I have followed the instructions for setting up the certificate store. I created a CRS file, and received my dev certificate from iOS. I also created a mobile provisioning profile and have received my .mobileprovision file from iTunesConnect. I then added these files to the certificate store in my services settings.

I should note here, the android build succeeds, I must assume there is a problem with my ios_development.cer file or my .mobileprovision file.

Does anyone have any suggestions?

I think I may have found the solution to my problem, I managed to miss this one important step in the documentation.

Next, we’ll need to convert the certificate from a .cer file to a .p12 file. It can be converted on Mac OSX by using Keychain Access and on other platforms by using OpenSSL.