A few teams, especially ones with large builds (400MB+) and slow-ish internet connections, seem to encounter the following error sporadically:
There was an error with signing your APK. Please try again or contact [email protected]
This seems to be related to a token timeout, so if you hit this, please try the following:
1) Refresh the page for the signing tool immediately before starting the upload to generate a fresh token
2) Upload again
3) Profit (hopefully)
Try this 2-3 times on as fast an internet connection as you can find, and start trying this asap (and not right before the deadline). It's better to submit an imperfect build than none at all.
Sorry for the frustration to those of you hitting this; we know you are working so hard and must be exhausted! You are almost there!