Are we talking about the same tool? All I do is select the tool, and click in the measure. Handles appear on the beam of whatever layer you are in.

If I recall correctly, the left handle adjusts the beam height, and the right handle changes the angle.

I've done that, and no handle whatsoever. Perhaps it's because I used the cross-staff part a bit too much? 

Make sure you are clicking in the origin staff for the cross staff notes, and in the correct layer.

I did that, and no go. I wish I could give you a screen shot or send you the file so you can see what I am up against, but...

Suffice it to say, I am frustrated. 

1) … When I click on the handle to see the prompt…nothing …

From your description it sounds like there is a handle (but clicking on the handle shows no prompt) - right?

2) … I've done that, and no handle whatsoever …

From this description is sounds like there is no handle - right?

What is the problem, exactly?

Is it 1) ? (= there is a handle, but nothing happens when you click on the handle)

Or is it 2) ? (= there is no handle)

No. 2 - there is no handle on the beam whatsoever. I've clicked the beam incessantly and no handle (little box) for me to move the beam.

Let us be scientific about this.

We need to know the steps you've already taken (to solve the problem), so that we can rule out things.

If I understand you correctly, you have already tried everything sugested above in this thread:

Make sure you are in the correct layer, and clicking in the origin staff.

What else have you tried?

Perhaps you have trashed the Preferences file?

Tried a new Windows user account?

Rebooted the computer?

I did, until I went back and found the problem, namely in the notes themselves. Went to the reverse stem tool, fixed some notes and then went to Beam Angle Tool which, this time, did work. Problem solved. 

Thank you, Peter and Mike. Sometimes you have to comprehend the instructions on how to cross beam and do it correctly, especially when you're sleep deprived. 

… Sometimes you have to comprehend the instructions on how to cross beam and do it correctly …

Or you could work smarter, not harder:

let the plug-in do the work for you.

Plug-ins menu > TG Tools > Cross Staff…