Please help with sonar

It's June, 1942 and I've just bought sonar for my VIIC. The problem is I don't know how it works. I get a contact and I have my periscope locked on it, but when I click on "estimate range to contact" nothing happens. All it says is "no contact selected" or something like that. What are the conditions for me to use it? Or is it a bug of some sort?


I've tried to manually do it myself, but when I take over the station, the (I think it is) sonar console looks like it's off and I can't seem to find the On switch. Help, please.