I keep got this error message on iPhone8:
"The developer needs to upload a build that supports your device's architecture (armv6)."
And the same version is ok to install on other devices (iphone7,6,ipad...).
So far I had tried
update mac to 10.12.6 and reboot
keep clean whole Xcode project
update crashlytics/fabric version
try Xcode 8.3 and 9GM
And nothing work for me.