Homeowners face numerous hurdles trying to get their mortgage modified. In some cases, applications are rejected with little or no explanation. It’s impossible to independently verify if a homeowner qualifies because the Treasury has not disclosed the eligibility formula used by lenders — a complex set of calculations that housing counselors and consumer attorneys have dubbed “the black box.” Housing attorneys report that some lenders are ignoring the program’s guidelines altogether and moving to foreclose without properly reviewing mortgages for possible modification. “It’s been a stubborn challenge,” said a Treasury official, who agreed to an interview but requested anonymity. “But this is something that’s never been done before.”