I experienced this same problem with a fresh install of 64-bit Precise. To resolve, I did:
sudo apt-get purge libreoffice* && sudo apt-get install libreoffice libreoffice-nlpsolver
So after uninstalling and reinstalling libreoffice and the solver, the extension is now there and enabled as expect. Hope that helps. This is still definitely a bug which should be fixed.
I experienced this same problem with a fresh install of 64-bit Precise. To resolve, I did:
sudo apt-get purge libreoffice* && sudo apt-get install libreoffice libreoffice- nlpsolver
So after uninstalling and reinstalling libreoffice and the solver, the extension is now there and enabled as expect. Hope that helps. This is still definitely a bug which should be fixed.