Fastlane stopped uploading my iOS app

Today I tried to upload a new version of my app, but it failed on iOS with a strange error: Unauthorized Access. It was strange because I did double factor authentication right, yet it still failed. Also, I'd expect it to ask me again if it had failed because of double factor authentication. Either that or ask me to sign in again.

But the Fastlane tool has a great little feature: it shows related GitHub issues, and sure enough, it seems like this error affected a bunch of people a few days ago.

So I updated fastlane using this command (read http://blog.wafrat.com/fix-fastlane-after-sierra-update/ for how I got it):

sudo gem install fastlane -n /usr/local/bin

And it finally successfully uploaded:

[11:03:07]: ------------------------------
[11:03:07]: --- Step: default_platform ---
[11:03:07]: ------------------------------
[11:03:07]: Driving the lane 'ios beta' ๐Ÿš€
[11:03:07]: ----------------------------------
[11:03:07]: --- Step: upload_to_testflight ---
[11:03:07]: ----------------------------------
[11:03:07]: Login to App Store Connect ([redacted])
[11:03:11]: Login successful
[11:03:12]: Ready to upload new build to TestFlight (App: [redacted])...
[11:03:13]: Fetching password for transporter from environment variable named `FASTLANE_APPLE_APPLICATION_SPECIFIC_PASSWORD`
[11:03:15]: Going to upload updated app to App Store Connect
[11:03:15]: This might take a few minutes. Please don't interrupt the script.
[11:09:16]: iTunes Transporter successfully finished its job
[11:09:16]: ----------------------------------------------------------------------------------------------------------------
[11:09:16]: Successfully uploaded package to App Store Connect. It might take a few minutes until it's visible online.
[11:09:16]: ----------------------------------------------------------------------------------------------------------------
[11:09:16]: Successfully uploaded the new binary to App Store Connect
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