Problem:
When retrieving a secret, the error popups, "Bad HTTP request with status 500." Showing the error details gives this information:
Cause:
This error appears when the secret's policy setting, Default Secret Challenge Profile, is set to "-Not Allowed". The default policy can be seen by browsing to:
Resources -> Secrets -> <secret> -> Policy

Resolution:
Modify the secret's policy such that the chosen profile allows the secret to be downloaded and/or viewed by the user.