hire an attorney. this practice is widespread in markets where the market crashed more than others. sometimes the sales don't meet expectations, costs get out of hand and the lender freezes the funds. it happens...
the problems is that halted construction will likely hold up the future residents from moving in
if yo have not moved in and just have a contract and deposit, get an attorney to try to sue for your deposit back.
if you're living in it already, I'd talk to some neighbors and try to get control of the HOA... then act as a group.

I recently saw this problem occur. Unfortunately, after some research I found the community was not being completed because the developer had gone bankrupt. However, another builder then bought the Community and was willing to give the current home owners their money back. I would definitely call the registrar of contractors to see if the developer is still financially able to complete the project.

You call the registrar of contractors or just even google the builder.