Android key signing on Windows for React Expo app?

I'm currently following this tutorial (https://medium.com/@inaguirre/react-native-login-with-google-quick-guide-fe351e464752) to add "Login with Google." I got the OAuth client ID working for iOS, but for Android, it requires an SHA-1 certificate fingerprint.
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I tried:

openssl rand -base64 32 | openssl sha1 -c  

and (I replaced the "path-to-debug-or-production-keystore" with the full file path)

keytool -keystore path-to-debug-or-production-keystore -list -v   

but neither of these work. A lot of advices given online is from the context of using Android Studio, but I'm using VS Code for an Expo app.

I get this error when I run the second, keytool command in the Command Prompt & PowerShell.

keytool error: java.lang.Exception: Keystore file exists, but is empty: C:\Users\User\Desktop\app
java.lang.Exception: Keystore file exists, but is empty: C:\Users\User\Desktop\app
        at sun.security.tools.keytool.Main.doCommands(Unknown Source)
        at sun.security.tools.keytool.Main.run(Unknown Source)
        at sun.security.tools.keytool.Main.main(Unknown Source)

I also tried running

keytool -keystore path-to-debug-or-production-keystore -list -v   

within the folder that contains the keytool.exe file within the Program Files/Java/jre1.8.0_241 folder, but same error.

Any help?
Thanks