Your trial version should automatically become the professional version as soon as you plug in the license key.
Has the key been re-programmed (upgraded) so that it is suitable for 15?
If not you will still only have the trial (demo) version.
Follow this link to check / upgrade your key.
http://www.archicadwiki.com/RemoteKeyUpgrade
Barry.
One of the forum moderators.
Versions 6.5 to 25
Dell XPS- i7-6700 @ 3.4Ghz, 16GB ram, GeForce GTX 960 (2GB), Windows 10
Dell Precision 3510 - i7 6820HQ @ 2.70GHz, 16GB RAM, AMD FirePro W5130M, Windows 10