PGP Command Line 10.x
Unable to decrypt certain files.
PGP Command Lines tried;

pgp --decrypt \\<path>\*.*.pgp --passphrase "passphrase" --temp-dir c:\pgp\temp

pgp --decrypt --overwrite rename \\<path>\*.*.pgp --passphrase "passphrase" --temp-dir c:\pgp\temp

Both of the commands above give the "3090: Operation failed, unknown error" message.

3090: Operation failed, unknown error

The encrypting party was changing the file name after the file was encrypted.
The file was encrypted with a signed key

Had the encrypting party modify the file name before encrypting.
The files can now be decrypted.