When processing encryption/decryption routines, exit code 64 exists
Exit code 64 represents a non-zero result, which ultimately means the encryption/decryption routine did not succeed.
Any non-zero result means something did not work properly. Each exit code should be reviewed in the PGP Command Line User's guide, but in most cases, only one scenario is known to be linked to exit code "64".
Typically when this is done, re-trying the encryption/decryption should be performed, but if any further issues happen as a result, more troubleshooting should be done.
If any further information is needed, reach out to Symantec Encryption Support.