McLeod wasted a host of chances against his former side before being substituted for the final half-hour of the League One clash at Fratton Park.
The striker is yet to score since returning to stadium:mk from Pompey but Robinson said: "Izale is going through one of those patches that all strikers have.
"It does not matter what he tries, the ball is just not ending up in the back of the net. I know once he scores one goal he will start hitting the net on a more regular basis.
"He is a great lad and we know from when he was here before what a good finisher he is so I am confident it won't be long until things turn around."
Veteran David Connolly gave Pompey the perfect start by heading in Jed Wallace's 22nd-minute free-kick to claim his first goal for the club.
But that lead lasted just five minutes before defender Shaun Williams struck a brilliant equaliser.
Luke Chadwick also came close for the visitors with a shot that shaved the crosssbar early on.
Robinson added: "That is three games in a row where we could have ended up winning but didn't.
"We were the better team for most of the game but the most important thing is to have commitment from the players. They are not shirking responsibility and nor are our fans."