You are probably soft banned.
Soft banning occurs when the game detects that you're moving around too quickly.
This can happen if:
You use GPS spoofing to fake your current location.
You travel in a vehicle at an excessive speed.
You disable your GPS, travel a significant distance, then re-enable it.
You lose data service, travel a significant distance, then re-connect.
The following are symptoms of a soft ban: When you throw a Pokeball at a Pokemon, it wiggles around a bit, then flees without fail.
When you try and spin a Pokestop, it never turns purple, and you never get any items.
You are unable to challenge or train at any gyms.
If you are soft banned, the ban will lift itself within a few hours .
Here's a video of what a soft ban looks like:
Currently, there is speculation that the soft ban mechanism functions similarly to the "bubble effect" in Ingress, the last ARG developed by Niantic.
This effect is explained here :
No matter what speed you are traveling, you can perform an action as long as you haven't performed one in the last 15 minutes.
Once you perform an action, a figurative "bubble" is created.
This bubble expands at the rate of 60 km/h.
If you travel out of this bubble, you will not be able to successfully perform actions.
So, once you slow down, you have to wait for the bubble to catch up with you before you can perform actions again.
After 15 minutes, the bubble goes away, and you can perform actions again even if the bubble hadn't caught up to you yet.
(For US readers, 60 km/h is approximately 37 mph.)
gaming.stackexchange.com/users/31508/Schism
It's quite possible that you were soft banned for moving too quickly.
The symptoms of not being able to get items from a pokestop and pokemon fleeing are exactly what happen when you are soft banned.
It should only last a few hours , and for some they're able to fix it by simply force quitting the app.
gaming.stackexchange.com/users/120054/Michael McQuade
If the game detects you are changing drastically varying locations too often, you will not be able to catch pokemon, and pokemon immediately run away when you do try to catch them.
This is most likely due to GPS spoofing or another cheat of some kind.
gaming.stackexchange.com/users/27903/Gigazelle
From my experience that means that you have lost connection to the game servers.
This can easily happen when you switch from home wifi to cellular network or kept the app open for some time (maybe in the background).
Another indicator that you lost connection is that the spinning Pokeball in the upper left corner never stops spinning and never disappears, when normally it would appear only for a few seconds and then hide itself again.
Most of the time you have to close the app completely (long press "home" or "menu" button on Android or use the app switcher button and swipe it away, similar on iPhones) and then start it again to make it work again.
gaming.stackexchange.com/users/138453/chrki
As you level up the Pokemon you come across have a higher CP (Combat Power).
This means that they'll also be harder to Catch.
You can use Razz Berries (you can get these from Pokeshops) to have a higher chance of catching the Pokemon.
Once you reach level 12 you also get access to 'Great balls' which will improve your chance of catching the Pokemon as well.
On top of this there are different ways of throwing your Poke balls which increase the chance of success.
The Pokemon Go wiki has some more details on Curve balls and the different Poke balls available.
gaming.stackexchange.com/users/154946/Bluerex
This may be an effect of a "soft ban".
Some one has completed some soft-ban research * involving spoofers and car travel.
A "soft ban" may not necessarily lock you out of the game entirely, only restrict certain features:
Penalties include: Inability to catch any pokémon, as they will break out and run guaranteed Pokéstops
become unusable Gyms
cannot be challenged (Battling or Training) One particular function to be aware of: Disabling GPS when in one place and re-enabling it at a distant location without allowing ample time for plausible travel could register you as "spoofing".
You could earn a ban this way!
Also using the same account with multiple devices that are large distances apart will also earn you a ban.
*
This is accurate at time of posting; it may be made redundant by future patches/updates
gaming.stackexchange.com/users/73976/Ben
Pokemons with higher CP are harder to catch, to help you can use berries and better pokeballs.
gaming.stackexchange.com/users/148364/Riley
I'm level 10 on Pokemon Go. I've caught at least 150 Pokemon, and had no problems. Now, every time I try to catch a Pokemon, no matter the level, it just rolls twice in the pokeball, breaks free, then runs away. Can anyone provide some insight on how to fix this problem?
Why can't I catch Pokemon in Pokemon Go anymore?
gaming.stackexchange.com
<pokemon-go>
gaming.stackexchange.com/questions/274315
gaming.stackexchange.com/users/154934/Wesley Schwartz
You are probably soft banned. It occurs when the game detects you're moving around too quickly. You may have been soft banned for moving around too quickly. It may also be a connection issue however.
Users suggest this may be the result of a soft ban Another user suggests it may be a loss of connection