When generating keystore during build expo is using keytool on our server, but when running opt-in-google-play-signing system keytool is used (it’s bundled with java SDK). For some reason, in your case it generated keystore in pkcs format instead of jks.
!!! Backup current credentials before doing next step
Run this command to convert it to jks(MY_FILE.p12 should be path to current jks file)
keytool -importkeystore -srckeystore [MY_FILE.p12] -srcstoretype pkcs12
-srcalias [ALIAS_SRC] -destkeystore [MY_KEYSTORE.jks]
-deststoretype jks -deststorepass [PASSWORD_JKS] -destkeypass [PASSWORD_KEY] -destalias [ALIAS_DEST]
run build:android -c and specify keystore and all the credentials manualy