Hi Tin,
Let's see how we can resolve your issue. By the way if you create a ticket at our UserVoice account we are able to respond faster:
User feedback voor Sleeve
In order to sync Instagram you would need to connect your account first, you can connect your Instagram account via settings -> import artists -> instagram (sync only, no artist import)
Could you try to resync your Facebook account? If you receive any kind of error could you make a screenshot and reply here (or uservoice)? You can resync your Facebook account via settings -> import artists -> facebook
Many thanks,
Orange Tribes