This issue can be resolved by reinstalling the ATP license to the ATP Manager. Changing the Cynic Sandboxing to "Use United Kingdom regional instance only", then un-selecting it also works. See: Cynic file submission failed
Currently it is not possible to submit files to Cynic that are larger than 10MB.
When submitting files to Cynic from the Advanced Threat Protection appliance, you receive different results if the file is slightly changed to alter the hash
Due to unpredictability of live malware, there is no guarantee of consistent behavior. Many viruses, trojans and worms attempt various actions based on a number of different criteria. The main focus should be whether the malicious verdict of the file is accurate or not.