Symfony multiple entity managers/connnections issue - symfony

Question

I have two symfony installations. One is a website and serves to store the users, sessions, account info, etc. The latter is an customer specific application install, with their own distinct DB and tables.
Authentication works fine on the main site. The idea being I could authenticate SSO and redirect the user back to their app instance.
I have managed to replicate my auth configuration in the application instances (mostly) how the application instances have slightly different doctrine config:
# config/packages/doctrine.yaml
doctrine:
dbal:
default_connection: default
connections:
default:
# configure these for your database server
url: '%env(resolve:DATABASE_URL)%'
driver: 'pdo_mysql'
server_version: '5.7'
charset: utf8mb4
account:
# Sessions and users are stored here
url: '%env(resolve:DATABASE_URL_SITE)%'
driver: 'pdo_mysql'
server_version: '5.7'
charset: utf8mb4
orm:
default_entity_manager: default
entity_managers:
default:
naming_strategy: doctrine.orm.naming_strategy.underscore_number_aware
connection: default
mappings:
App:
is_bundle: false
type: annotation
dir: '%kernel.project_dir%/src/Entity/Core'
prefix: 'App\Entity'
alias: App
account:
naming_strategy: doctrine.orm.naming_strategy.underscore_number_aware
connection: account
mappings:
Sso:
is_bundle: false
type: annotation
dir: '%kernel.project_dir%/src/Entity/Shared'
prefix: 'App\Entity\Shared'
alias: Sso
This works - kinda - until Symfony tries to authenticate. The user entity is being retreived from the application DB, which does not have the Users table.
I thought the above ORM configuration made this obvious? All other scripts (schema:create, etc) seem to work...what am I missing?!?
EDIT security.yaml
security:
#enable_authenticator_manager: true
providers:
# used to reload user from session & other features (e.g. switch_user)
app_user_provider:
entity:
class: App\Entity\Shared\User
property: email
firewalls:
dev:
pattern: ^/(_(profiler|wdt)|css|images|js)/
security: false
main:
anonymous: true
lazy: true
provider: app_user_provider
#custom_authenticators:
# - App\Security\SessionAuthenticator
# activate different ways to authenticate
# https://symfony.com/doc/current/security.html#firewalls-authentication
# https://symfony.com/doc/current/security/impersonating_user.html
# switch_user: true
# Easy way to control access for large sections of your site
# Note: Only the *first* access control that matches will be used
access_control:
#- { path: ^/admin, roles: ROLE_USER }
# - { path: ^/profile, roles: ROLE_USER }