Issue with Sync button missing in Modern Document Library.

[Orion-Skol]

So recently the sync button disappeared for sites and document libraries in modern UI.

In classic they are still there and the sync works. It seems to be only for publishing sites. Anyone ideas?

I check following options and both are enable (Yes):

STEP #1
Go to the site affected collect > “Site Settings” > “Search and offline availability”
Change the option “Offline Client Availability” to YES

STEP #2
Go to the Library Settings > Advanced Settings
Change the option “Offline Client Availability” to YES

When I created new sites, no luck there with modern ui.

Any idea or thoughts??? Some users in my company complain same situation...

[#2]

@Orion-Skol I have two tenants both of them its appearing and even when I alter the offline availability setting they are responding as intended. I would assume somehow related to your tenant.

In admin message center I see this notification not sure if that is somehow related.

I will follow if you get to the resolution.

Thanks

Vik

[#3]

@Vikram_Samal good find on message center. Suppose this related with this new feature or tenant issue, whom should i contact....? 

[#4]

I will suggest to open a case with the MS and get their help. As you might be aware each tenant has different release so you need to understand what has changed for you.

Thanks
Vik

[#5]

@Orion-Skol If you have MFA enabled for everyone, then external users can lose their sync button.
https://docs.microsoft.com/en-us/onedrive/b2b-sync

"Multi-Factor Authentication from an external organization is not yet supported. Only guest accounts that don't require MFA will sync."