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.
[Procedure 1]
After updating to Illustrator CC 2018, reboot the personal computer.
[Procedure 2]
Boot the Creative Cloud and select [Apps] tab. Click menu at right side of [Open] button..
[Procedure 3]
Select [Other Versions] in the displayed menu.
[Procedure 4]
After clicking [Other Versions] button , the installable former version is shown. Select the version that you install.
[Procedure 5]
After installing Illustrator, install FineCut/RasterLinkTools.