I had a similar thing happen with my DO cloud domain. @DrFran and I both made our’s at the same time except her’s is a $10 one with a placename located on the east coast US and mine is a $5 one with no place name on the west coast. Her’s seems to work fine, the default content shows up and things work as expected.
Mine is unusable. The default content does not appear, just a few cubes, a red platform and some particle mist. Eventually the unloaded default content times out and green outline boxes appear. Looking at the server nodes in domain settings, I can see the asset server blink off and on again, crashing and restarting.
Loading an externally hosted (S3) model seemed to work OK so I thought I would look at ATP assets and tried to open the asset browser window like @Skimi did above. I got the same error message window which then I could never close.