OK guys i fixed the problem finally. For anyone who has the same problems, this did the trick (at least for me):
- Uninstall UE4.18
- Uninstall Codeworks for Android
- Delete all the remaining folders of UE4.18 & Codeworks for Android
- Reinstall 4.18, make sure to close any projects AND the launcher after installation
- Reinstall Codeworks for Android with the installation file which comes with the 4.18 release (Folder: Epic Games\UE_4.18\Engine\Extras\AndroidWorks\Win64) follow the official installation instructions (https://docs.unrealengine.com/latest/INT/Platforms/Android/GettingStarted/1/)
- After installation goto this folder: \NVPACK\android-sdk-windows\tools and run “android.bat”
- There click on “Deselect All” at the bottom and scroll down to “Extras > Android Support Repository” click on the checkbox and on the install button on the button right, then accept the licenses (THIS IS IMPORTANT) and finish the installation
- Open up your project, pack your game for android and it should work now