Well, never created the keystore myself, but I've compiled a aab with a keystore many times, so it definitely should work.
Try verifying files integrity on Steam and if you're not on the beta, try using it.
Here's the info about keystore and stuff on Fusion:
- Keystore name Enter the pathname of the keystore that contains the key to sign your application. To generate a keystore you can use the Keytool tool provided in the bin directory of the JDK. This is a command line tool. For example, the following command line will generate the "d:\great-release-key.keystore" file that contains the "great_key_name" key: keytool -genkey -v -keystore d:\great-release-key.keystore -alias great_key_name -keyalg RSA -keysize 2048 -validity 10000 Keytool asks you for your name, organization, country, the keystore password and key password. More info here.
- Keystore password Enter the password of the keystore that you have entered when you've created it.
- Key name Enter the name of the key that will be used to sign your application. See above for more info.
- Key password Enter the password of the key you have entered when creating the keystore.