Infrastructure changes introduced in CA 2.x, downgrade from CA 2.x to 1.x is not supported; a factory reset would be required.
When downgrading from 2.x firmware to 1.x firmware a factory reset will be required.
Downgrade Support:
Because of infrastructure changes introduced in CA 2.x, downgrades from
CA 2.x to 1.x are not supported; a factory reset would be required.