The spaces overlay provided does not include any network space bindings for the mysql-router charms - I suspect this may be the cause of your issue as the network address resolved via the endpoint binding in this charm is used to generate the ACL (and must match at both ends to actually work).
That said the example spaces overlay does not include bindings for all applications either so that does need to be updated.
@hyperbaba
The spaces overlay provided does not include any network space bindings for the mysql-router charms - I suspect this may be the cause of your issue as the network address resolved via the endpoint binding in this charm is used to generate the ACL (and must match at both ends to actually work).
That said the example spaces overlay does not include bindings for all applications either so that does need to be updated.