Sidechain in channel strip compressor not working

Hi i have a question, when i activate the sidechain of the compressor inside the default channel strip ( not in the inserts), and i select the channel of the source, nothing happens, no signal is detected, but if i put the same compressor in the inserts chain and i activate the sidechain, it works perfectly. Can you tell me why please? Sorry for my bad english, hope you understand me
Cubase 12 pro / win11

It’s working as expected here. How did you “select source”?

I think,you need to press ALT + click to add signal to the sidechain.

(Sorry about my english)

Make sure that the send is not too low.