keystore not found for signing config ‘release’.– React native

The problem in this case is the path. As you have already mentioned above, enter the key in the app folder.
Then in your .properties, don’t name the whole path, because you are already in your project / app .. you just have to enter the name of the key:

storePassword=my_password
keyPassword=my_password
keyAlias=key
storeFile=key.jks