Help with sonar - "no target selected"

[ET2(SS) Pallak]

Hello, this is my first post. Love SH4. I am running 1.5 with TMO 2.0, and I am trying to make the transition from auto targeting to manual TDC use.

The problem I am having is this:
I am currently trying to attack a lone merchant ship at night in stormy weather. The ship can only be seen using the scope at a range less than 300 yards (too close to fire upon) so I am attempting to find a firing solution using sonar only. My sonar operator has no problem following the target and continually gives me a bearing of the merchant ship. Whenever I try to use active sonar to find a range to the target, It tells me "No target selected." If I go to the sonar station and ping manually, it sends a outgoing ping, but nothing is returned. How do you select a target with no scope?
I have looked through multiple tutorials, including the werner sobe sonar only tutorial, and I cannot find what I am doing wrong. (Maybe Werner Sobe just has a much more competent sonar operator. lol)

Please, if you have any insight as to what I am doing wrong, let me know as this is driving me crazy; it is probably something simple that I'm going to kick myself for.

I apologize if this question has already been asked and answered; the search engine for the site leaves a little to be desired (But isn't that true for all search engines any more?).