Previous to February 2017, snapshots might require extra time to be pulled into active storage but would return a "Snapshot not found" message, even though the snapshot was indeed found but just loading.
To prevent this erroneous message, TrustedForm now sometimes returns a brief "Retrieving Certificate" message, even on brand new Certificates, while the snapshot is loading to active memory.
This message should disappear within 30 to 90 seconds and your TrustedForm certificate will load.
As of February 2017, when a TrustedForm certificate is viewed and returns the "Snapshot not found" message, it's very likely that the associated snapshot was not uploaded to TrustedForm storage when the certificate was generated and is indeed missing.
For more information see "Why is my TrustedForm snapshot missing".