Ahh, let's see...
The antenna was the first thing I broke on my car

I also used to push it down, and one day I payed for it. Literally, I had to pay for a used one from a guy with a wrecked diesel engine.
The power antenna has this plastic cable-like thing with "teeth". My guess is that you broke it. I did the same, and I almost succeeded in putting it back (after shortening), but it was *such a PITA!* And it didn't work - it's impossible to fit the cable to the thinnest (top) part of the antenna securely if you don't work for Nissan
So you will need either a new power antenna, a used power antenna, a new non-power antenna, or a nice antenna that is glues to your rear window (you call it Euro

) and shave off the original hole ($$$). I would prefer the latter option. I believe someone has done this before on this forum, but I can't find it.
Good luck
P.S. Guys, never push your antenna down!