I am unable to login to Vuforia Studio after upgrade. It has JSON parsing error while logging in by ... and Settings > Portal Login. Attaching Logs for more information.
There is a similar thread in some way with an error - "Can't Publish since updating to Vuforia Studio 8.3.4": https://community.ptc.com/t5/Vuforia-Studio/Can-t-Publish-since-updating-to-Vuforia-Studio-8-3-4/td-p/575527
Are you still using a Vuforia Experience Service trial instance ?
This Portal Login menu is only available for trial, not for environment hosted on premise or in PTC Cloud.
Actually I am trying to login in Vuforia Studio. And have downloaded the instance of it from here > support.ptc.com > Login using my creds > Download Software > Vuforia Studio, following latest release for mac or windows.\