Robinson was frustrated as his side carved out a string of chances but only managed to score from one deflected effort, the League One clash ending 1-1.
Coventry, without a home win this season, took the lead in the 34th minute when Richard Wood powered home a header from Gary McSheffrey's corner. But they could not keep the lead for long as Stephen Gleeson tried his luck from the edge of the area and the ball struck William Edjenguele and flew into the net.
"They started very well and caused us problems in the first 10 minutes, but after that I thought we were magnificent," said Robinson. "It was criminal of us to concede off a set-piece but I was pleased with the way we retained the ball and our wingers caused a threat but we did not take out chances.
"We had enough chances really to have won four games. Our front six players got more than 100 goals last season but it did not go for us here at all. They are not bad players, they are just having a barren spell.
"Not many people will come here and win. Mark Robins (Coventry manager) will turn this around as he does with clubs, and this will be a hard place to come and play. We should have got more from the game and it is a bitter pill to swallow."