I followed the installation instructions for Fedora 28 described in Linux Setup Guide, but I noticed that it still lists version 1.4.5. Is there a reason why your repositories are not up to date ?
dnf list insync
Last metadata expiration check: 1:32:33 ago on Sat 22 Sep 2018 08:08:42 AM EDT.
Available Packages
insync.i686 1.4.5.37069-fc25 insync
insync.x86_64 1.4.5.37069-fc25 insync