Q: Copy - paste problem

***??? Why is this not working??
Why is apple not responding. THIS IS ABSOLUTELY BASIC, ANY CRAPPY PHONE WOULD BE ABLE TO COPY AND PASTE... but my $600+ iphone 6s can't...

And don't you dare give us a copy paste answer telling us to reset our phones.

I think the option should still be there.  If this happened since you bought an iPhone 6s+, you might find that it takes some time to get used to the 3D Touch feature (pressing too hard or not hard enough).

Change 3D Touch sensitivity on your iPhone 6s or iPhone 6s Plus - Apple Support

I was sure that was not it but I still went ahead and tweeked the sensibility. SAME problem.
The opcion of copy appears but paste doesn't when I try to paste it.

Sometimes when I copy twice it works but not always. If fails with every app.

Same issue: IOS 9 copy and paste does not always work

Well, I'm afraid I can't think of anything else except the stock answers.  One of which is to take it to an Apple Store and let them look at it.