[USA] My stepfather had $500k+ crypto stolen; he hired a private investigator who identified the thief's wallet on Binance. All he needs now is a subpeona; but the FBI nor Secret Service will help. What can we do?

Background context: My stepfather has been investing in crypto for about 4-5 years. At the time, he primarily used Coinbase. Around the start of 2021, he had an issue where he had got locked out of his account. He was trying to get back in and was getting no response from support.

Naively, he tried to Google "coinbase support phone number". Unsurprisingly, scammers had flooded the results with fake sites with phone numbers posing as Coinbase. Sadly, he fell for one of the fake numbers and was phished out of his credentials and all of his crypto was stolen. The value of it was around $500,000 to $750,000 at the time it was stolen.

I was not as involved in my stepfather's crypto up to this point (though I wish I had been), but once he confided in me what happened, I have been trying to help him on attempting to recover these assets.

I helped my stepfather audit a reputable private investigator firm that specializes in crypto theft recovery. Throughout the past year and a half, they have been tracing the paper trail of the thief.

The firm was eventually able to trace the stolen crypto to a wallet on Binance. In order to proceed on recovery, the firm requires my stepfather to obtain a subpoena from a law enforcement agency in order to move forward.

My father is located in Indiana. County and state refuse to touch crypto because they don't understand it. The only remaining options are the FBI and Secret Service.

The private investigator provides full written instructions for my stepfather and for the law enforcement agency to follow (who to contact, what to say, etc). Once the subpoena is obtained, the PI will continue to work on reclaiming the stolen assets following. However, they cannot until a law enforcement agency signs off.

My stepfather has been trying for over 6 months to reach out to the Secret Service and FBI, but nobody will listen. Understandably, it's excruciatingly frustrating for him because it's been tracked back to an individual wallet; but the information about it cannot be obtained because law enforcement won't cooperate.

Is there anything I can do for my stepfather to get the FBI or SS to cooperate on signing off on a subpoena? Cases have been filed with both offices but nobody seems to care.