Conditional Formatting for a spilled area

[Es123]

Hello,
I try to use conditional formatting for data I grabbed via an external method from my DLL. I've done this with single or even multiple columns quite often, works always as expected. No fancy stuff just using Color Scales from the menu. Suddenly with one spilled area it doesn't work. I've tried using another sheet, specific cell formatting, no formatting and no other conditional formatting rules, not working either. The functionality leading the formula seems to have no effect.

Searching this problem on the net I've found that conditional formatting isn't possible for spilled areas (only with a trick). I'm running the subscription which is Microsoft 365 and it seems now it's possible.

Is there any case I'm not aware of when this conditional formatting is not possible?
Thx for any hint

 

[Es123]

So this is what I want to format at the original place in my sheet. As one can see the second row has formatting via ColorScale (conditional formatting). This is the only conditional formatting rule I use for that area. Another conditional formatting the other rows seems not be possible. The cells have format number. I guess there's something easy I must miss here.