Does not seeing the Prophet, peace be upon him, in a dream after a supplication specifically for this vision mean that God is displeased with the servant, or that there are impediments to the acceptance of the supplication?

Supplicating to see the Prophet, peace and blessings be upon him, is permissible, and its answer may be delayed for a wisdom known to Allah. Better than that is to supplicate for steadfastness upon his Sunnah and adherence to his guidance, for this is the path to salvation. Not seeing the Prophet does not mean Allah's displeasure; rather, one should be occupied with obeying Allah, performing the obligatory duties and supererogatory acts, and dedicating one's actions sincerely to attain His pleasure and love.