I also had this issue with some floor plans I was working with. It seems that it was caused because the exporting program (AutoCAD perhaps?) placed the resulting graphics within oversized clipping masks that were larger than Illustrator's pasteboard - which also made it impossible to even see that the graphics were contained in clipping masks. Using one of the comments below of using the Transform tool and reducing the size of my graphics to 10% also reduced the size of the clipping masks, making them small enough that when I zoomed out I was able to see them.

In my case, once I saw what the issue was, the simple solution was to use the Direct Selection tool (white arrow) in Illustrator rather than the Selection tool (black arrow). By selecting my content this way, I was able to copy only the content that I wanted, omitting the oversized clipping masks. Once copied, I was then able to easily paste the content into my other document without any issues.

Hope this helps!

thanks @Carlee W - worked for me too! Clear guides.

ADOBE.
PLEASE RID OF THE RESTRICTED SPACE TO ELIMINATE THIS UNNECESSARY ISSUE.
WE SHOULD BE ABLE TO PASTE ANYWHERE AT ANY TIME.
AND MOVE IT TO ANYWHERE WE WOULD LIKE.
IF YOU WANT TO KEEP THIS UNNECESSARY ISSUE, AT LEAST PROMPT US WHEN SAVING.
UNTIL THEN, LET ME PASTE WITHOUT ISSUE.

WASTING SO MUCH TIME.

@Carlee W: Thank you! That did it for me as well.

for some reason, i had this problem only tied to a certain image file. no matter what format I saved it on Photoshop, I couldn't import it to a particular AI file. Then I tried inserting another random image, which was in a higher resolution. It worked. Then I opened the compatible image in Photoshop, pasted my intended image upon it, flattened and saved, then inserted into AI. Of course it worked. This shortcut might come handy.

I can't even scale down the object using the transform option.

This is extremely stupid. What kind of useless issue is that.

I pressed "View" > "Guides" > "Clear Guides" which solved it for me.

Hopefully this helps anyone still running into this issue.

One suggestion/trick to bypass this annoyance is- before copying the object, scale it down to 10% of it's original size (possibly more depending on how large the asset is), and then paste it into the new document and scale it to 1,000%. If the scale tool does not work, use the Transform panel and link the height and width and type in the correct height or width. Also to move this object after it's been pasted and scaled up, you may have to use the X and Y coordinates in the transform panel to actually move the object to the desired location on the artboard.

I'm having the exact same issue!