What you have mentioned is totally confusing.
Actually based on that GPA, the power agent purchased the property on behalf of his principal.
However for selling this particular property which is actually stands on the name of the principal of this power agent, the principal has to execute a fresh GPA to this power agent with the mention of the schedule of this property in the fresh general power of attorney deed, otherwise this power agent is not authorised to sell the property to which he is not authorised to sell.
Any such sale is invalid and not binding on the principal if he disclaims the same in future.
However you may consult a local lawyer on this further details.