Hello. Today I'm going to show you how to fix the service error.
There are few methods known yet, if there's going to be any new, I'll update this guide.

All methods were tested by me, most of them worked, but not all. It's all depending on your system and graphic card (AMD is more problematic than NVidia)

Method 1,7 and 8 seems to work in most cases. Try them first.

Method 1 : After entering the game, leave main screen open. After few minutes (3-5) click play online. It should fetch your profile without problems.

Method 2 : Check your NAT status. Make sure it is not set to restrict, it has to be open.
Tutorial to open your NAT step by step:
1. Search for ''cmd'' in windows
2. Open it!
3. Type in "ipconfig"
4. Find your IPv4 Adress
5. Go to your Libraries
6. Find Network
7. Go to "Network Infrastructure"
8. Right click-Properties - Settings
9. Add a service
10. Name it (however you want)
11. Type your IPv4 adress (From step 4)
12. Change to UDP
13. Type "3074" on both ports
14. Press "OK"

! If you dont have network infrastructure go down to the bottom right of your home screen right click on the internet icon -> open network and sharing centre -> change adapter settings -> your network -> sharing option !

Method 3 : Make sure your servers are running at http://www.callofduty.com/advancedwarfare/status/

Method 4 : Check your connection:
1. Restart your router.
2. Turn off programs that transfers large amount of data (such as uTorrent)
3. Launch windows troubleshoot problems

Method 5 : Review your IP: (not all routers have support)
1. Go to http://www.whatismyip.com/
2. Paste your IP into the browser
3. Sign in and disable port forwarding
4. review extra settings

Method 6 : Disable network sharing: Control panel -> Network sharing -> your internet connection -> Connection status -> Properties -> sharing -> Uncheck both Internet connect sharing boxes, make sure you're not sharing

Method 7 : Compatibility settings (Credit goes to: 1WILDC4RD)
1. Go to your install location ( "C:\Program Files (x86)\Steam\steamapps\common\Call of Duty Advanced Warfare" By default )
2. Search for multiplayer .exe program (s1_mp64_ship by default)
3. right click -> properties -> compatibility
4. Select Windows Vista in "run this program in comparibility mode for" box and change to Windows7

Method 8 : Background connections (Credit goes to: lilguybc and Mr.Flashout)
1. Open any YouTube video in background (In - steam web browser ,accesable by pressing "shift + tab" or try other types of background connections.

Method 9 : Enable firewall (Credit goes to: SlovakianGamer)
1. Open Windows Firewall (Start button -> Control Panel -> Turn Windows Firewall on or off)
2. Click Turn on Windows Firewall under each network location that you want to help protect
3. Click OK

After trying all those methods, I hope at least one helped you to connect succesfully.
If you know any other method, leave a comment. (I'll test your method)