This started happening a while back, maybe around 2.3, after a fairly major update, but I used to have sraidframes setup to show warlock castable buffs, and this included SS. At some point, an update was released to the addon, and I can no longer get SS to show up.
I have it set to show buffs castable by me and my class, and I can see just fine when I cast see invis or water breathing on someone. But I can no longer see who has soulstone. I even added it to the "always show these buffs" list ("Soulstone Resurrection"), and that didn't help.
Anyone have ideas? It was very convenient to see who had SS.