How can we get our EB-5 investment back?

You should consult a lawyer near the location where the promoters of the invest live. You may have to sue them.

You should review your contract and consult a lawyer. You might have to sue them for your right. Violation of Immigration law does not necessarily mean the contract is void. It is an executed contract, a judge may order in your favor depending on what the contract says.

You need to look at the subscription agreement and see what the provisions are for repayment and if they lied, you need to provide it in securities litigation.

You need to consult an employment law attorney in the state where the project is located. It is not illegal to get your money back and most projects do this. It depends though on the terms of the agreement you signed with the project.

Its possible but it sounds like to recover the money you may need to file a lawsuit.

The terms and conditions of your investment with the EB-5 project are contained in the written agreements signed between you and the project. It is unlikely that any advertisements, agent, or project representative statements to you before you invested regarding a "guaranteed return" will be honored, since such guarantees are not in the written agreements. You do have certain rights, however, which should be explored and protected. You should consult with an experienced EB-5 attorney who can advise you. It is unlikely any return on your investment or litigation to seek return on your investment would have any effect on your green card since you already removed your condition.

It is your money. Talk to an investment lawyer.