Answer: After that state had ratified it
Step-by-step explanation:
Even though the Constitution required only 9 out of the original 13 states to ratify it for it to become law, a state was only obligated to follow the Constitution after they had ratified it.
Ratification by a state means that the state has formally approved the Constitution and so by giving this approval, they agree to follow the Constitution and so will be obligated to do so.