I think I have the same problem as you and I think it's a permissions / service issue.
I can actually get it started, despite the fact the installation from the dash or from (ssh) root fails with "cp: cannot stat '/root/QuickBox/setup/templates/sysd/syncthing.template': No such file or directory"
If you ssh in, switch over to root and start syncthing (just type 'syncthing' from the command line) it should start the service. With the SSH session running, you should be able to then browse to the Quickbox dash and start the syncthing gui with no problems. It's obviously not a fix, but it seems to highlight where the issue might lay.
The syncthing service refuses to start with my normal user. It only accepts root. Would love a solution to this problem. I'm just getting in to linux and I'm still not up on troubleshooting services
ps: should add, am also on ubuntu 16.04 running v2.94 of QB