As of November 2015, Chase now requires users to have a Client User ID, and use header version 103. These instructions for GnuCash were found on the GnuCash user's list:
On Ubuntu I created a UUID in a terminal with
uuidgen. One can probably edit ~/.aqbanking/settings/users/<xxx.conf>
directly, but I used the wizard.
It always takes me a while to find where the aqbanking settings are
within gnucash; so here it is.
Start Tools/Online Banking Setup, Forward, Start AqBanking Wizard, Edit
User, User Settings, then paste the UUID.
Then in the same Edit User dialog, select Application Settings, and set
the Header version to 103.
I then downloaded some data (not all), so I then logged onto the web
site, read the secure message and activated the
account. Now it's working.