email - Thunderbird :: Stuck at Google sign-in (xenial)

Can't get past this thunderbird dialog:

even though less secure apps are enabled:

Thunderbird is explicitly allowed:

Mozilla Thunderbird Email
Has access to Gmail
Homepage: 
https://www.mozilla.org/thunderbird

Has access to:
Gmail
Read, send, delete and manage your email
Access given on:
26 July 2016

The version is 38.6.0 so cannot see why a ppa would be necessary, particularly when the version installed is greater than that suggested. Potentially, re-installing a plug-in would fix this.

System:

thufir@doge:~$ 
thufir@doge:~$ cat /etc/lsb-release 
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=16.04
DISTRIB_CODENAME=xenial
DISTRIB_DESCRIPTION="Ubuntu 16.04 LTS"
thufir@doge:~$ 

The "more options" button's background animates, but does nothing.

Probably switching from OAuth to "regular password", per one of the other answers in linked questions, would work.