Same issue here on Safari. This problem has always been there but could be resolved by erasing browsing data. But now, nothing to do it just won’t fix it.
When I preview my app I get a message in the console : User not logged in and cannot view this app in the editor - cannot see debugger
with a link:https://dhtiece9044ep.cloudfront.net/package/run_debug_js/b60458350f5b2105dc420d2b04901b1fa608dbc017bef6a686fcec9f91e20f53/xfalse/x5