Symptoms

When trying to access View Flow, you receive the error: ArgumentException: ID2057: Cannot construct a X509SigningCredentials instance for a certificate without the private key.
Parameter name: token
 

Diagnoses

View Local computer certificates (via mmc.exe andgt Add snap-in andgt certificates andgt Computer Account andgt Local Computer) on all nodes and locate the K2 self-signed certificate that does not have a private key (it will be missing a key icon in the left corner).
 

Resolution

Export the identical K2 self-signed certificate that does have a private key from another node (be sure to export it with the private key), and import it on the failing node.