View the photos from the Blues' latest League One stalemate
Pompey battled from behind against Bristol Rovers to draw their fourth league match in succession.
Jonson Clarke-Harris netted from the spot after Tom Naylor had controversially been adjudged to have fouled the striker.
But the Blues were level after the break when a delivery from Ronan Curtis was turned into his own net by James Clarke.
Clarke-Harris then missed the chance to secure victory for the visitors, blazing a second penalty high over the crossbar.