Nextcloud 13.0.6 in stable does not upgrade to 14

[Schmu]

That’s the same for every update:

@jospoortvliet

If you want Nextcloud 14 but prefer to use the updater, note that it will take time before Nextcloud 14 is available there. We roll out incrementally, that is, today only 20% of the Nextcloud installations gets notified. If no problems are found, we will add another 20% or so later this week and probably go full out next week. Patience, or manual installation!

So you have to wait for the next update wave and check again. Your second server will probably be within one of the next waves then. If you want the update instantly, you have to perform a manual update.