Error fetching data for this visual

For anyone with a similar issue, we had an "overview" report with row level security that was sourced from multiple workspaces that was giving this error. When looking at the cloud connections, I noticed that there was a connection to a report in our DEV workspace (no end user access) that had the same name as the intended report in our PROD workspace (end users have access), and that was the cause. So the overview report had either been built using the DEV report connection and never switched over, or the report had been inadvertantly set up to use the DEV report instead of the PROD report.

I wouldn't expect this to be the case in every situation, but we were stuck for a while trying to figure this out, so I figured that it could help. The gateway/cloud connections do seem to be the right direction to pursue.