Can you help me figure out how to get ANY Userstyles to work with Fluid?

[jasonnmark]

I plugged this into code inspector in Safari and it worked fine, making things bold:

.xY {
    font-weight: bold;
}

So I tried this

and nothing happens (big font size and color are just to make it super obvious). I also tried your gmail code verbatim and nothing worked. I can't get Fluid to seem to change anything.

I'm using Version 2.1.2 (2120) on an M1 Mac running 12.3.1

Does anyone see an obvious thing I'm missing?