FIPS Mode Issues

Why does Adobe Reader DC not recognize and allow a user to digitally sign documents that are password protected as FIPS compliant when FIPS mode is enabled in the registry?

The password protection uses AES256 block ciphers which is FIPS compliant and the digital signatures on Windows 10 are signed using a SHA256 hash, both of which are FIPS compliant. Reader does notbseem to agree because per the Adobe site and FIPS mode description, it only sees SHA1/2 as FIPS cryptograohy methods.