Yes, I use the same method as you to initialise my HISM component.
I then call [Update Instance Transform] in the [Event Tick] path to update the rendered HISM objects.
It’s weird.
My asset is working, but for some reason in 5.5.1 the ‘spawned’ HISMs only appear after clicking a UE editor UI element ‘outside of the viewport’ as shown in the video link.
Why would that make the HISMs suddenly appear? No idea, but UE 5.4.3 and before never had this issue.
Note: this isn’t a [x]‘Mark Render State Dirty’ issue.
Just as a sanity check, I checked/unchecked the option on all my [Update Instance Transform] calls, but it made no difference.
I don’t think the issue is with my blueprint (I can’t see how), nonetheless, I will strip down my blueprint to it bare minimum functionality to replicate the issue in a very basic project.
Hopefully, UE dev/support will investigate and have some thoughts about what is going on.