Hi, Kris – thanks for getting back to me so quickly!
We were using version 1.3.2 of the Guardian SDK but recently encountered a similar, but different, issue with Safari that was basically the same as this issue (“cannot connect to real time channel”). In looking at the repo on Github I noticed there was a version bump to 1.3.3 that included some default transport changes that was never published to NPM, so tried upgrading to that by manually pointing the SDK to github:auth0/auth0-guardian.js#81de93a0f8e760cb4cc8c018fc5c0fb3faa554c3, which seemed to fix the Safari issue. (separate point – could Auth0 publish the 1.3.3 release to NPM?)
Our client is experiencing the issue in Chrome 79.0.3945, and, since my original post, I have been able to confirm with the client that forcing the Guardian SDK to use https://{custom domain}/guardian as the serviceUrl does, in fact, resolve the issue. Our team has not been able to replicate the issue internally, so there seems to be a browser policy blocking the cross-domain request (the client is on an enterprise network).
It seems to me like using the custom domain (rather than an auth0.com domain) would be a much more reliable approach, and I would very much like to release this to production, but don’t really want to be using an undocumented/unconfirmed URL in production.
Thanks very much for your help!