When should I sync the blockchain?
Your Bread connects directly to the bitcoin network. This improves security and privacy, but also means sometimes your Bread can get out of sync with the network.
Syncing with the blockchain can take a lot of time, and usually isn't necessary. If someone sent you money and it shows as confirmed in the blockchain yet it is not appearing in your wallet, your wallet may be out of sync. First check to make sure the address the money was sent to is correct.
If you are trying to send money and constantly get error messages that your transaction was rejected, it could also mean your wallet is out of sync.
In either of this cases, using this feature will rescan the blockchain to find your money and display it properly in your wallet.