If you do not have a "target", none of the dials will move. If you are in Manual-targeting mode, you do not get the triangle. If you are in a Single Mission (or Sub School, Multi-Mission, War Patrol), you use the Main Menu's "Options"
... and "Gameplay Settings" choice.
... to clear the "Manual targeting system" box in the lower-left column
If you are in a career, when you are in the Captain's Office while at home port, use the radio console to the left of the screen as in:
... to access the "Options" menu
... and then "Gameplay Settings" to clear that same menu choice for Manual-Targeting. That will get the green (orange or red) triangle back. Then, when you "lock" onto a target, or get the triangle near a ship and press the PTT button (that currently "white" button at the bottom right of the Position Keeper box), the dials will move for you. When lit "white", as below, the PTT is off. When lit "red", it is on. The "Lock" light (on the lower-right torpedo box) lights when you are "locked" on a target. Both Manual and Auto targeting are the same in that regard.
If instead, you are looking to "manually input" targeting data with the "Manual targeting system" enabled, then you use the TDC dial on the right-hand side of the screen to input range, AOB and speed, and when "updated" will move the dials on the left. Or you can use Nisgeis's
3D TDC and Radar Range Unit for the Gato and Balao in the Stock game (which is really cool), but a bit complex. However, you will not see a triangle in Manual mode...
btw - Happy New Year!!! lol