The defeat by Hull was a fourth in five Championship games in April as the Sky Blues lost momentum at a crucial point.
They twice equalised after the Tigers went ahead, but had nothing left in the tank following Noah Ohio’s 78th-minute goal.
It means they will not make another trip to Wembley, having also lost the play-off final to Luton Town last season.
“We know why it is,” Robins told BBC CWR. “We can’t afford any injuries at all and when you get those, it has cost us dearly.
“At the end of the day, we’ve had a real go at both competitions. It’s been a brilliant effort from everyone, but we’ve come up just short.”
