It seems this is a fastlane issue / caused by a recent change (2018 March 01) on the iTunes Connect API. See: https://twitter.com/kenyonj/status/969226546526523392
As suggested there the solution can be to specify the DELIVER_ITMSTRANSPORTER_ADDITIONAL_UPLOAD_PARAMETERS env var to the value -t DAV
You can set this in the Workflow Editor, on the Env Vars tab:
- key:
DELIVER_ITMSTRANSPORTER_ADDITIONAL_UPLOAD_PARAMETERS - value:
-t DAV
This should fix the this issue.