Clash of Clans is extensively tested before each update on several device types internally, within Apple's Software Development Kit, as well as by Apple themselves during the update approval process. There are times however, where some user's devices encounter issues after initial install, update, or server maintenance. Here are some self-help steps to try if you are encountering issues. Some of these steps or menu paths may be different or not available on every iOS version.
PLEASE ASSOCIATE YOUR VILLAGE WITH GAMECENTER! VILLAGES NOT ASSOCIATED WITH GAMECENTER (ONLY LINKED TO THE LOCAL FILES ON THE DEVICE) CAN BE VERY DIFFICULT, AND ON OCCASION IMPOSSIBLE TO BE RETRIEVED IF YOU LOSE ACCESS TO THE LOCAL FILES.
1) Jailbroken devices are not fully supported. If it's jailbroken, we can't help you. Return the device to original configuration to fully enjoy Clash of Clans.
2) Close the app an relaunch it
From the home screen, click the home button twice (or do the 4-finger swipe upwards) to show open apps. Press and hold until the red "-" appears. Click that to close the program. Press home to exit that screen.
NOTE: For iOS 7 users, double click the home button, swipe each app picture upwards to close.
3) Power off and/or reset your device
Press and hold sleep button until power off swipe displays, then power off or
Press and hold both sleep button and home button for 10 seconds until Apple logo appears.
4) Remove the app and re-install it (Make sure your game is connected to GameCenter or you could lose your village!!!)
Click and hold on CoC icon until icon jiggles and "X" appears then click it to remove. Press the home button to stop the jiggling/exit delete mode. If the icons don't start to jiggle, make sure "Deleting Apps" is not turned off in Settings>General>Restrictions
5) Upgrade your device to the latest iOS version it supports
Either via your iTunes sync or over the air for iOS 5+ (settings>Software Update)
6) Check that your device is not full (settings>general>usage) Make sure you have several MB available for temp or update files.
7) Reset your Apple ID Authorization by simply installing any free app that isn't already on your device. You can remove it afterwards if need be.
8) Log out of Gamecenter or Facebook (if linked) and log back in. You can disconnect from Facebook in-game if you can access the game. To log out of Gamecenter open it, click "me" at the bottom, then click the banner that says "Account: your account" then "Sign Out". Log back in 1 at a time if on both to see which, if either is causing the issue.
9) If your device utilizes syncing with a computer through iTunes, try syncing.
10) Ensure your Date/Time settings and Time Zone are correct.
Settings>General>Date & Time
11) Do you have a good network connection that is allowing TCP traffic over port 9339? Some public hotspots do not have this open. Here is a quick URL to check: http://portquiz.net:9339/
12) If you suspect network issues, you can reset network settings: Settings>General>Reset>Reset Network Settings
12a) Try an alternate connection method. Switch from cellular to wifi or vice versa. Try a neighbors (with permission) wifi, preferably with a different ISP.
12b) Cycle the power on your Router.
12c) Replace your ISP's DNS server with Google's public server: 126.96.36.199
Make note of what you currently have before you change.
Settings>Wi-Fi>blue > symbol after your SSID's name> DNS
Replace your current settings (after you write them down) with 188.8.131.52
If this works, then your ISP's DNS server is not updating in real-time
13) If your device was issued through work or school - There could be issues with any profiles installed via Mobile Device Management programs, Apple Configurator, or content filtering. Check with your work/school IT Department to further investigate.
14) Check the crash logs - may provide a clue: Settings>General>About>Diagnostics & Usage>Diagnostics & Usage Data> Within that list, any CoC ones should start with "Clash of Clans_then date There is lots of techie stuff in there, but some plain text info near the top that may help
15) Contact your Service Provider. If the above steps didn't help you, 99% of the time, it's an issue with your ISP. Some providers either unintentionally or for specific reasons mis-catagorize Clash of Clans network traffic. Several major ISPs do or have blocked the game in the past either all the time or during specific times of the day. Contact their customer support and explain your issues to them to see what they can do.
16) You can always do a factory reset (Not recommended without being linked to gamecenter)
Recommend doing an iCloud backup first then restore from iCloud backup - make sure
Settings>iCloud>Doucments & Data is turned on. You can further check that Clash of Clans is specifically being backed up by clicking Settings>iCloud>Storage & Backup>Manage Storage>Backups (your device name will be here) under "Backup Options" confirm CoC is "on" For older devices, you can do a backup through iTunes. This should be the last option. If your village is not linked to gamecenter, this step is not advised as you will lose access to the locally stored village files.
If none of these steps help you, These are your next best options. It is helpful to already know the following - most of which can be retrieved through: Settings>General>About
*iOS device model - iPad (1/2/3/4/mini), iPhone (iPhone/3G/3GS/4/4S/5), iPod Touch (1/2/3/4/5th gen)
*iOS software Version
*Utilizing wi-fi or cellular
A) If the crashes happen in-game, where you can access the game, Click the Settings icon, then Help and Support button, then "Report an Issue" button. This is important, because it sends the e-mail with in-game account data needed to better help you.
B) E-mail support directly with as much detail as you can to: firstname.lastname@example.org
C) Make a forum post in the "Bugs & Problems" sub-forum. The first thing we are going to ask is did you try the steps in this Sticky, so please indicate that if you did. When making the posts, Please include model/ios/connection type as well as what point the app fails/crashes and as many details as possible.
**If anyone has found any other steps helpful that I forgot, or I have something worded wrong in this, feel free to PM me so I can update to better help others.**