Hi Abhishek,
So,
Desktop: I go to the already sync Vault at my Desktop which is connected (with 171 items). But there's no 'Setup Sync' option. Please see attached Image "1".
Mobile: I am not sure what to restore. Shouldn't I delete something first before restoring? There is already a Dropbox vault with the same email adress as with that with the desktop, but as said only 155 items here.
Please note that I've already removed the app, and re-assigned the vault, which restored 155 items instead of 171. So my guess is an error from the side of the Desktop device.