This letter proves that the FBI is required to process NFA appeals and it is not doing so. Please take a look. Instead it is telling the ATF to do so but the ATF is not conducting appeals because it is not allowed to by law. Page 4 is the important page.
Basically there is a fight between the ATF and FBI https://www.scribd.com/document/449774915/Umbert-ATF-FBI-Letters
Basically there is a fight between the ATF and FBI https://www.scribd.com/document/449774915/Umbert-ATF-FBI-Letters