If Illustrator CC, CC 2014 is already installed in your personal computer when updating to Illustrator CC 2015, the former version Illustrator CC, CC 2014 is delated and you cannot use FineCut/RasterLinkTools.
Please follow the procedure to reinstall the former version Illustrator CC, CC 2014 and enable FineCut/RasterLinkTools.
[Procedure 1]
After updating to Illustrator CC 2015, reboot the personal computer.
[Procedure 2]
Boot the Creative Cloud and select [Apps] tab. Click [Filters & Versions].
[Procedure 3]
Select [VIEW PREVIOUS VERSIONS] in the displayed menu.
[Procedure 4]
After clicking [Install] button at right side to Illustrator icon, the installable former version is shown. Select the version that you install.
[Procedure 5]
After installing Illustrator, install FineCut/RasterLinkTools.