We apologise for the delay, our dev team are still investigating the issue and for some users we are suspecting this issue:
A cookie associated with a cross-site resource at http://prismic.io/ was set without the `SameSite` attribute. It has been blocked, as Chrome now only delivers cookies with cross-site requests if they are set with `SameSite=None` and `Secure`. You can review cookies in developer tools under Application>Storage>Cookies and see more details at https://www.chromestatus.com/feature/5088147346030592 and https://www.chromestatus.com/feature/5633521622188032.
Meaning that if that is the issue then it can be due to a change on chrome side that will require some changes of the way we create preview cookies.
But we are still investigating the issue that the other users having, and we let know if have any updates.