react-native run-android command terminates by leaving a message in android simulator. The message is as follows:
Unable to load script.Make
IMPORTANT - You might have many Virtual devices in your environment. Ensure if you are changing AVD you repeat the setting again.
Incase you are experiencing above error you have to 1st verify what is running on port 8081
Quickest way to find that is using the following command in terminal
netstat -aon | findstr 8081
if that shows you something it means the port is blocked. if possible get that port unblocked.
Otherwise, you would need to change the port. The process to do that has already been mentioned in the comment above by Naveen Kumar
react-native run-android --port=9001
Ensure 9001 is not used either :)