Copy/Paste

I am trying to copy/paste data from one complex workbook into a separate, completely unlinked second workbook. As you might expect, I can copy the data without a problem, but when I go to my second workbook, Paste, and even Paste Special are grayed out. Help! Sorry, no pictures allowed.

Is this the case for every Excel workbook? Have you tested by creating two new workbooks and attempting this?
Some alternatives: (copy/paste in Excel is not reliable - as you've witnessed)

Use Data > Get Data > From file > Excel workbook in the second workbook to pull the data from the first.
Power Query to pull the data into the second workbook.
This could be done with VBA as well from either file, from the source to push the data to the second workbook or pull data from the first workbook into the second.

Try moving whole sheet.

In first workbook right click on sheet name where is your data stored
Move or Copy...
Check box Create a copy
Choose from drop down menu To book: New workbook book

Then in destination workbook you can delete undesired data