So I’ve seen two instances of this:
One of these is in Chester situated at The Cross (53.190233,-2.891534). It does very occasionally spawn in for a few months before disappearing again. Chester though is full of sponsored stops and gyms because of an event that took place there (which are amazing to have), and I think the sponsored gyms may have affected it coming in and out.
The second one is in Estepona (36.426799,-5.141756). This sculpture used to be situated at Plaza De Las Flores but when the Plaza was refurbished a couple of years ago the sculpture was moved to a new location which is in a different level 14 S2 cell. A few years ago I added new photos and requested it to be moved to the new location via the help chat (location >10m edit), all of which were accepted, but it didn’t respawn in the game after the move as it was in the same Level 17 cell as something else. However it did have a lot of photo upvotes and since then we’ve had more wayspots be added in that Level 14 cell. However no new Gym has spawned and it looks like it’s triggered this and because it doesn’t spawn in the game we’re likely not going to get one, so I guess you can blame me for that partly lol xD, but a bit odd that it didn’t pick a stop that spawned in the game. It was a PokeStop when I requested the move too. 
Indeed Escultura La Elefanta Requetebien in that cell is officially live but inactive, it will count as a gym, but won’t be in the game.
Same problem for The High Cross, Chester
I’m going to split this into its own topic as this is marked solved.
It does show on the pokemongo map as a gym.
But is not eligible on the wayfarer map.
It is interesting that it sometimes appears.
I think the nearby EE sponsored gym is an issue.
It counts as the 3rd gym in that level 14 cell so there no “missing gym”
The Chester area with the missing Gym has several sponsored Gyms in it’s place (and stops too), so that may be the reason it’s popping in and out. These were added as part of the Chester Heritage Festival Event in 2017. EE is also sponsored but was added later on. Interestingly God’s Providence House (53.190155,-2.892245), Grosvenor Museum (53.187346,-2.892487) and Chester Castle - Agricola Tower and Castle Wales (53.185609,-2.892340) are also showing as an inactive Gym in this area, but again lots of sponsored Gyms here.
It’s no problem if The High Cross cannot be readded as a Gym because of these, and I also wouldn’t want to readd this Gym for the sake of losing the sponsored Gyms, as that wouldn’t benefit the community at all and I think they’ll be some very unhappy players (and I’d also feel guilty about that).
There are also Community Ambassador Stops and Gyms in Grosvenor Park, which like the sponsored stops are not affected by cells, but it hasn’t affected the original number of Gyms in these cells and these are just additional. though as far as I’m aware there have been no location edits to these existing Gyms as of yet
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Regarding Estepona, Hopefully it will be possible to add a third Gym, even if it means passing the Gym on to the next highest upvoted photo in that Level 14 S2 cell that appears in the game.
Hey @MikeySeedot ,
Thanks for your feedback. We’re constantly making improvements to Pokémon GO and occasionally, you may notice changes to the PokéStops or Gyms in your community. While we are not able to fulfill your request to add back these locations at this time, we recognize the disappointment this may have caused and hope you continue to seek out adventures at other PokéStops and Gyms in your surrounding communities.
Thanks,
