Appium error

Error: Could not find a connected Android device

Appium's UiAutomator2 driver couldn't see any device or emulator through ADB when the session started.

Why this happens

No emulator is booted and no physical device is connected/authorized
ADB itself isn't running or lost its connection to the device

How to fix it

Confirm the device shows up with `adb devices` before starting the test, and fix ADB/USB debugging authorization if it doesn't
For emulators, make sure the AVD is fully booted (not still on the splash screen) before launching the session
Restart the ADB server if it's stuck: `adb kill-server && adb start-server`