While I'm surprised of the reply to your service ticket, this is a bug that can also be found in your O365 Admin center, see attachment.
Title: "Sync" button not visible on Modern UI for some sites.
User Impact: Users are unable to see the "Sync" button when using the Modern User Interface (UI) within some site templates.
More info: This issue does not affect site templates for OneDrive for Business, Teams or Groups. While we're focused on remediation, users can switch to the Classic view UI, which is not affected by this issue.
Current status: We're investigating an issue in which users are unable to see the "Sync" button within some sites. We're reviewing site data in order to troubleshoot the issue and to develop a plan to mitigate impact.
Scope of impact: A few customers have reported this issue, and our analysis indicates that users accessing the affected site templates using the Modern UI may be impacted.
Start time: Monday, February 27, 2017, at 12:00 AM UTC
Next update by: Monday, March 13, 2017, at 9:00 PM UTC