I ran into the same problem when I integrated Fastlane with Crashlytics. I wanted to distribute the assembly for testers.
In Fastlane, you can choose whether you want to publish the Debug APK or Release the APK. Fastlane is trying to publish an APK release. I just changed it to debug the APK in Fastfile, and it worked.
I'm sure it can have some settings in Jenkins that can publish Debug APKs. hope this helps.
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