Trainers, Pokemon Go went under a server maintenance today for some time, and according to Niantic announcement, the game is back up, but the game is not working properly as the maintenance is not fully completed.
Here is the official announcement from Niantic:
Global downtime update:
Trainers, we are slowly starting to reopen access into Pokémon GO to ensure game stability. However, if you log in during this transition time, you may experience odd app behaviors, such as being unable to see Gyms or PokéStops on the map.
For this reason, we strongly recommend that all Trainers refrain from accessing the app at this time until maintenance is fully completed. We’ll be updating again when that is. Thank you all again for your patience!
So if you log in, you will not see any PokeStops, Gyms or Pokemon spawns at the moment.
They will fix this soon, so stay tuned for more details.