I have launched my emulator via the AVD manager and once it's running I have clicked on
choose a running device
Probably the project you are running is not compatible (API version/Hardware requirements) with the emulator settings. Check in your
build.gradle file if the targetSDK and minimumSdk version is lower or equal to the sdk version of your Emulator.
You should also uncheck Tools > Android > Enable ADB Integration
If your case is different then restart your Android Studio and run the emulator again.