Bruno Mars fans were left disappointed when they were forced to miss part of his concert because of ticket problems.
Some took to Twitter to express their anger and disappointment following the event at Birmingham's Barclaycard Arena on Monday.
The venue has apologised and has invited fans to lodge complaints.
Lisa Kerry, from Walsall in the West Midlands, said it was an "absolute joke" after being left outside the venue because tickets would not scan.
Ms Kerry said there was "no explanation from management".
"We missed the support act and the first hour of the performance," she said.
"Hundreds of people had been left waiting for a couple of hours."
Leanne Hulse, from Tamworth, took her sons aged five and eight to what should have been their first gig - after their aunt paid £400 for four tickets for their Christmas present.
After they queued from 19:00 and were turned away, Ms Hulse said they would never go to the venue again.
Karen Paterson said she bought tickets for her daughter's 16th birthday and drove from their home in Burlton, Shropshire - only to queue for three hours before being refused entry when there were problems scanning tickets.
She said she was "angry and disappointed".
Gregg Nicholson, from Birmingham, said he only saw half the concert.
"I think the phrase in the queue was 'raging'. Everybody was of the same mindset," he said.
The Barclaycard Arena apologised to customers affected on Monday and said it had "plans in place to mitigate any potential issues" ahead of another concert by Mars there, on Tuesday night.
It said it had re-issued tickets to standing customers in March specifying whether they were in a front or rear standing block but it "acknowledged that the customer communications to support this update were not sufficient".