UPDATE 3/09/2021, LATER IN THE DAY: Ron Bates correctly pointed out that this registry key is referring to the UI for hide/show decals in the viewport - if I toggle it, I see the behavior I was experiencing. However, since it doesn't appear to hide/show decals in the viewport, it appears to be broken. I think this decoupling from the viewport is probably what made it so hard to troubleshoot.

UPDATE 3/09/2021: Problem solved - Edit the registry, Computer\HKEY_CURRENT_USER\SOFTWARE\SolidWorks\SOLIDWORKS 2020\General\Hide Decals in SW render, change value from 1 to 0

Thanks to Sarah Kemp at TriMech for figuring this out for me.

Of course why there should be such a specific registry key and where that option gets ticked outside of the registry is a question yet to answered....

I'm trying to add decals to a part - doesn't matter if it's a new or existing part or decal. I can add the decal, and while I'm editing it shows up in the preview. However, once I'm done editing, it doesn't show up in the preview or the final render. It is visible in SolidWorks.

I'm running SW2020 SP3.0

UPDATE: I updated my video driver to the latest version with no change, and then installed the specific driver version listed for my system on the SW recommended driver list, which also did not resolve the issue.