What should I do if the regional center does not refund my investment after an I-526 denial?

This would be governed by your contractual agreement with the regional center, which would be spelled out in the terms of what would happen in case of an I-526 denial. If the agreement states a refund within 90 days, without exception, then you should pursue legal action to recover the funds.

You should carefully review offering documentation (PPM, etc.) with an attorney. This is a matter of contract law under the jurisdiction of the state where documents are executed. An attorney can send a demand letter and, if unsuccessful, file a lawsuit to recover funds.

Consult an attorney to pursue whatever remedies are in your contract, including, but not limited to, a lawsuit.

If the regional center does not refund your funds after your EB-5 investor petition on Form I-526 is denied and, if per your written agreement as set forth in the various documents, including the private placement memorandum, they have an obligation to refund the money within 90 days, you should consult with your attorney and your attorney should send a demand letter to the regional center setting forth the legal basis upon which they are obligated to refund your investment. Your attorney should seek an amicable resolution, but if they still refuse, you always have the right to sue the regional center in order to obtain a refund of your investment.

That is a matter of contract law. A corporate/business attorney may be able to assist you.

Review the documents carefully to evaluate your rights. Unfortunately, because of the long time to adjudicate petitions, many projects are now deploying the funds and it appears only some have holdback escrow that cover such refunds. Others, apparently, do not.

You can sue the regional center for violation of its own contract if the regional center is in violation of a clause that allows it to retain your investment until a substitute investment is located, or you can sue it for violation of the Securities Exchange Act for failure to disclose risk of loss. The federal government, i.e., the Securities and Exchange Commission, may also come to your aid.

You should read the contract closely to understand all scenarios with regards to I-526 denial and make sure you are following proper procedures for requesting the capital. You may need to get an attorney to help you understand the contract. Then you should meet with securities and litigation attorneys to understand your rights under the law.

File a lawsuit to recover the funds.

The exact details of the agreement for a refund will probably be governed by the offering documents (subscription agreement, PPM, etc.), and you or an attorney would need to review those. From a practical perspective it sounds like the regional center is trying in good faith to find a way to refund you the money. Lawsuits are slow and expensive, so the fastest way to get your money back may just be to wait for them, even if it is longer than they promised. If you do not think they will find a replacement investor, then you may want to look at other options.