Photoshop won't allow more than one image to be open

[jageez]

I reinstalled Adobe CS6 on one of my old computers (MacOS10.14.6) to teach my niece some Photoshop basics. 

Unfortunately, every time we open a new image when another image is already open, Photoshop closes the first image as it opens the second one. It won't allow multiple images to be open at the same time. I haven't seen this behavior before on any version of Photoshop; it never happened when I used CS6 many years ago. 

Is there a setting somewhere that is set up wrong? I haven't been able to find it.

[c.pfaffenbichler]

Are you sure the first image is closed? 

Is it still listed at the bottom Window > …? 

What have you done for all-purpose trouble-shooting so far? 

Restoring Preferences after making sure all customized presets like Actions, Patterns, Brushes etc. have been saved might be a good starting point:

https://helpx.adobe.com/photoshop/using/preferences.html

https://helpx.adobe.com/photoshop/kb/basic-trouble-shooting-steps.html

[jageez · Accepted solution]

Thanks, the problem has been solved.