Drag and drop into new files

[#1]

I used to be able to have 2 different documents open in Illustrator, select what I wanted from one file and then just drag and drop them into the other file by hovering over the tab at the top. 

It's now not letting me do this - is it a setting I need or something? 

Still fairly new to Illustrator 

[#2]

I used to be able to have 2 different documents open in Illustrator, select what I wanted from one file and then just drag and drop them into the other file by hovering over the tab at the top. 

It's now not letting me do this - is it a setting I need or something? 

Still fairly new to Illustrator 

[#3]

Click and drag the item to the other document's tab, which shifts the focus to the destination document. When that happens, drag the cursor into that document and release. Works fine for me. It's not clear to me if you are dropping the object onto the tab, which would not work.

Peter

[#4]

yep thats what I used to do and I'm currently still trying to do that but the focus never changes now, only started in the last 2 weeks.