Hey sam.mcgoldrick1, turns out, my problem was indeed the NodeJS version.
But Konrad forgot to tell us where to look on Auth0 tenant settings (and it comes with the Node 4 set, and even with the “deprecated” label)
Change here at the bottom to version 8 https://manage.auth0.com/#/tenant/advanced
Delete the Bitbucket/Github extensions and re-install.
It worked for me.
(Still not sure if this was your initial problem…)