There are lots of posts here that are similar to what I'm working on, but none of them gave completely applicable answers to our situation.
Last year I created a couple of reports for Splunk license usage on our DMC which I then embedded in a dashboard on our SHC for management. It worked fine on our 7.3 SHC and I never had to do any of the embedSecret or allowEmbedTokenAuth changes I see other people referring to.
In first quarter of this year we built a new 8.0.1 SHC on beefier Linux hardware and we discovered yesterday that those (and other) embedded reports do not display. The embedded links all still work if you use them on their own in a browser and I've even tried disabling then re-enabling the embedding of the source report then using the fresh iframe code over on my SHC dashboard.
I don't see anything relevant in the release notes (although I've been at this about 10 hours, so maybe I'm not seeing straight anymore).
Can anyone point out whatever stupid mistake I've made?