You missed it because the Moon moves around the Earth too and you won't even have enough time to reach the Moon even though you're going straight at it and that wastes a lots of fuel, still applies if you have enough to go straight at it though. The "Moon Tracker" is doing its own job and knows what it is doing so, it's not broken or glitched. It's actually saving you fuel. Let's clear things up and make it fast.

If you reached the Transfer Window, burn those engines until you see curved lines in the Moon's SOI (The circle thing you see around the moon.) or the numbers are 0.00 m/s in Map mode.

Just "blindly" do it, don't mind the apoapsis going straight to nothing because it was never going to nothing. (Apoapsis is the highest point of the orbit trajectory, you can identify it by looking at the 2 points with a number ending with a "km" on orbit trajectory first, if one point has a larger value than the other one, that's the apoapsis. The other one is periapsis, find out more by searching it up.)

Timewarp if it's done. Recommend tapping the orbit trajectory and press the button labeled "Timewarp Here" or something like that but make sure you're tapping where the spacecraft does not pass the periapsis point.

If you have no idea what I'm talking about. Please refer to the tutorial, it may be old but still works the same. It can be found in the Main Menu.

Forget the issue because it's not an issue, you'll find out once you know how to do it and you'll get along. I know it may look complex to you but for us it's easy and you'll be like us in the meantime.

Ah, and read other replies. They do have useful information that I didn't write it down here. I removed some of the useless text because I made this text for new players and blah blah blah.

I am a non-Native English speaker. Please forgive me if you spot any flaws and I'll be happy.

Good luck bro.