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.
insync.i686 22.214.171.124069-fc25 insync
insync.x86_64 126.96.36.199069-fc25 insync