If Illustrator CC-CC 2017 is already installed in your personal computer when updating to Illustrator CC 2018, the former version Illustrator CC-CC 2017 is delated and you cannot use FineCut/RasterLinkTools.
Please follow the procedure to reinstall the former version Illustrator CC-CC 2017 and enable FineCut/RasterLinkTools.
After updating to Illustrator CC 2018, reboot the personal computer.
Boot the Creative Cloud and select [Apps] tab. Click menu at right side of [Open] button..
Select [Other Versions] in the displayed menu.
After clicking [Other Versions] button , the installable former version is shown. Select the version that you install.
After installing Illustrator, install FineCut/RasterLinkTools.