This is in the 8.2 ADXStudio Microsoft portal release. If you have issues with any entityview or fetchxml liquid tags on a web page or custom javascript that previously worked, and now mysteriously returns no data after an upgrade, check your entity permissions for the logged in contact.
This is (to my knowledge) an undocumented change in the way these tags behave. You have to create an entity permission with at least READ access for the primary entity that the view or fetch is retrieving. This permission needs to be related to a WebRole, which is then related to the authenticated contact. I simply used the Authenticated Users role and set a global "Read" permission for the entity. That could potentially cause side effects of exposing too much data, but in our case everything is additionally filtered to prevent that.
I just wanted to help the next poor soul before they go through the hours of trial and error that I did to discover the solution. Thanks to Adam Hong for pointing this out here:
https://community.adxstudio.com/forums/adxstudio-portals/68465eea-2806-e611-9407-000d3a10c65c
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