@RomanZ i went on the page you suggested (http://help.getsync.com/hc/en-us/articles/206215185-Synology ) but it didn't work.
Beside the DS115 which now seems working after automatic updates, on the other side of the sync I have a DS415 Play, which should mount a x86 architecture if I'm not wrong:
I tried to upgrade BT Sync from version 2.0.93-1 to the latest version available 2.3.6-1
From the support page you linked, I tried the manual installation of the package
https://download-cdn.getsync.com/2.3.6/Synology/bittorrentsync_x86_2.3.6-1.spk
But I get the error message "This package is not supported".
Am I missing something? The package I choose is the right one for my platform? If not, what should be the right package to use? If it is the right one, why it isn't working?
Thanks for your support that is better than the official synology support.