adb.exe: no devices/emulators found

This error message appears when the adb (Android Debug Bridge) tool is unable to find any connected devices or emulators. There are several reasons why this might happen:

1. USB Debugging is not enabled on the device: To enable USB Debugging on your Android device, go to Settings > Developer Options > USB Debugging and turn it on.

2. The USB cable is not properly connected: Make sure that the USB cable is properly connected to both your computer and your Android device.

3. The device drivers are not installed: If the device drivers are not installed on your computer, adb will not be able to recognize your device. You can download and install the drivers from the manufacturer's website.

4. ADB is not installed on your computer: If you have not installed the ADB tool on your computer, you will need to download and install it from the Android SDK website.

5. The device is not in the correct mode: Make sure that your device is in the correct mode (e.g. MTP, PTP, or USB Mass Storage).

6. The device is not supported: Some older Android devices may not be supported by the latest version of ADB. In this case, you may need to use an older version of ADB.

7. The adb server is not running: Make sure that the adb server is running on your computer. You can start the server by opening a command prompt and typing "adb start-server".