When you look at the nearby Pokemon the screen shows that there are 9 nearby and all are 3 steps away. No matter which direction you walk and how far, all Pokemon are still 3 steps away and nothing is showing up. This appears to be an issue with the game and not the server. It would seem that your phone can only track 9 Pokemon at once. When this tracking glitches it fails to refresh and remove Pokemon or query the server for a refreshed list. This gets incredibly frustrating when you are in the process of tracking a rare, unknown Pokemon to complete your collection. The sad news here is that its likely a glitch and the Pokemon is gone.
The location of Pokemon is shared across all players in the area, specifically the rare ones. If you turn the game off and force restart it, the Pokemon will still be there if it is legit. Most of the time it’s going to be a situation where the game has gotten screwed up and there isn’t actually a Pokemon in the area.
There is no fix for this other than a forced restart of the game. If you restart and the Pokemon are gone, then you know it was caused by this bug. If they are still there then you should be able to correctly track them now and hopefully be able to catch whatever you were after.
Try to keep an eye on this if you are out walking. It can get annoying when you have walked a few Km only to discover the game has glitched out and no Pokemon are going to show up in your area.