Approved Stops approved but not visible for month
I have created some new stops a few month ago (3 stops in July). Somehow these stops, even though they are approved, are not set live in Pokémon Go.
At the same time stops that were approved a few month after are already visible and one stop was set up as a arena.
Are there additional criteria influencing the Pokémon stops after being approved or what is the reason for this system behaviour?