I can tell you from personal experience ATF does not care about this kind of thing. I talked to several agents and couldn't get any to do anything about it.
I can tell you the only hope you have is local law enforcement. Call the local sheriff dept and find an officer to talk to. I did this (and luckily he was also a gun collector) and he paid a visit to the person and made notes after talking with them. Then talk to the DA- these people often have a criminal history or repeat this more than once and get slapped on the wrist. The local DA can go after the person for I forget the wording but something like "tampering with governmental record (FFL) with attempt to defraud"
i gave ATF the emails with copies of drivers licenses, the phony FFL and even 8-10 recorded phone calls and texts from the culprits- but they didn't care! I even had restricted delivery certified mail receipts with their signature matching the drivers license signature exactly. I led them on to get all the info from the criminals. One of the ATF agents actually knew when I first started talking who the fraudster was as they had been doing this for over a year and been getting tons of calls. The fake ffl and drivers license scan matched the address of the residence and the IP address from the emails that the local sheriffs officer went and visited for me. The sad thing is part of the scammer group started forging C&R licenses which can't be verified on the online check- allowing them to receive firearms by mail illegally!!! I tried explaining this to ATF again they didn't care. ATF says they won't go check out the mailing address because they say nobody will be there or it's an abandoned property. In my case the officer went to the drivers license/ fake FFL address and talked to the person directly face to face.
I have run across this now several times since in my collecting activity and have just ignored it, sadly one of the recent cases involved someone trying to pretend to be our friends at knob creek.
sorry if I am out of place in the post but please try the sheriff/DA. ATF doesn't care. Just be persistent and find an officer even if you have to call and talk to multiple officers, on multiple days, eventually you will find one to listen. Happily I can report one of the fraudsters who was already a multiple felon is in local county jail now on a 2 year fraud sentence from the local charges no Fed time or federal charges but hey I'll take that, sadly I bet they are out in 6 months doing it again.