The InDesign Application Frame gets stuck outside the screen area/behind menu bar

This issue has just happened to me and I found a solution that works. I haven't seen this answer in any of the replies above, so apologies if it's duplicated.

I have 3 screens, and InDesign was stuck on the laptop screen.

So, here goes:
Go to InDesign > Preferences > User Interface Scaling.

My settings were on small so I scaled it to large and clicked OK, it will come up with a message saying "Changes to your UI scaling settings will take effect after you restart InDesign", I clicked 'restart now' and it automatically reopened InDesign and was 'moveable' again, and I just went back into UI scaling again and repeated the steps above changing back from large to small and everything is back to normal.

Phew (panic over)

Current InDesign version: 18.0

Current MACOS: Ventura 13.0.1

God Bless

However - I have a user this happening to, and she's never used a monitor. She is opening files locally and off the network that may have been access to coworkers using dual displays.

I've gon through all the steps listed - and the issue persists.

Mac Os 10.14.6, Indesign 2021 ( 16.4)

any other ideas?

I know this is an old post, but the problem persists, and I just found a simple solution; at least it worked in my case. 

First, note that I work with my large external monitor positioned above my laptop screen. I'd guess that this is a pretty common arrangement, and it's inconsistent with the "correct answer" below.

Many people (on various sites) suggested turning off and on the Application Frame. That didn't help me: with or without the frame, before and after, I still had the same problem. 

But then I simply closed InDesign and reopened it again--still the same problem. But THEN, when I turned the Application Frame off and back on again, the frame was freed up from its anchored position and I was able to move it around at will. 

I'm having this same problem, I have two screens and have aligned them in the Systems Prefs so they are side-by-side as mag-man suggests then closed and reopened InDesign but it's still off the screen. This solution doesn't work. Mac os 12.2.1

Was having the same problem however none of the suggestions were working.

So I was thinking it was at the OS level.

~/Library/Preferences/ByHost/com.apple.windowserver*.plist

I moved it to my desktop and added OLD in the filename 

Then restarted the machine and it worked. It seems to me that the external monitor settings got stuck

I hope that this helps

Thank you a million times over!!!

What happened to me is this:

I had 2 monitors connected to my MacBook Pro using Indesign 2021. I disconnected the monitors, took my Mac on a 4 week trip with no other monitors availabe. Now i cant use InDesign because it don show on my MacBook.

How to fix this?

Thank you mag-man, that worked!

Thank you for sharing this info! 

I'm having this same problem but none of the suggested solutions are working. My InDesign application window is stuck to the top of my screen, whether I'm using two monitors or one, I've tried resetting the workspace, oriented the other monitor "below" the primary monitor, restarting InDesign, nothing is working. I will try deleting the InDesign Preference File. I'm using a MacBook Pro with Mojave 10.14.6 and Id CC 2020.

Follow-up: I deleted the InDesign Application Preference file and restarted. When I opened Id again, it was just a pile of dismembered toolbars and control panels, even after resetting the workspace. I finally went to Window > Application Frame and selected it (so it is checked) and then everything was restored. Super disruptive and tedious.