I just upgraded my DS918+ to DSM 7 last weekend. I installed the x64 version from the Resilio website as you pointed out. I had previously used Sync under DSM6 but had to do a full reinstall of the app via the DSM interface. I had an issue when trying to access the setup page using Chrome due to the self-signed signature. I was able to get the page to load by typing 'thisisunsafe' which overrides the security warning. I was also able to access the page using Safari. Not sure if that is the issue. The other thing I would try is to access the Resilio page using the actual NAS IP address instead of xxx.synology.me:28888, use IPADDRESSOFNAS:28888 and see if that loads the page.