The ID token error is unrelated to state. I’m not sure exactly why that was happening but we’re adding better error handling so, at the very least, you get a better failure message. Login will still fail in that condition but it will give a more helpful message. Tracking that here:
https://github.com/auth0/wp-auth0/pull/492
For the invalid state problem, I put together some detailed debugging steps here:
As mentioned at the bottom, if those do not resolve the issue, please post back here a complete HAR file I can take a look at.
Thanks for your patience while we get this figured out together!