NJ.com – More than a week after online gambling began in New Jersey, casinos and their partners are still struggling to verify the location of people who want to play on the new websites. Steve Callender, the general manager at the Tropicana Atlantic City, said about 75 percent of people who have tried to play on the resort’s online gaming website — TropicanaCasino.com — have been denied because the system could not verify they were in New Jersey. “I would say a quarter are getting on,” Callender said yesterday, noting there’s a positive side to that: “We don’t have a…