Why are Heketi commands failing with 'Invalid JWT token: signature is invalid (client and server secrets may not match)' after an OCS upgrade?

Issue

• After an OCS upgrade, any heketi-clicommand fails with the below error:

  heketi-cli --user admin volume create --size=1
  Error: Invalid JWT token: signature is invalid (client and server secrets may not match)
  

• The provisioning of Gluster volumes doesn't work either for the same reason. The command oc describe pvc <pvc-name>shows:

  Persistent Volume Claim Warning Provisioning Failed     Failed to provision volume with StorageClass "gluster-default": failed to create volume: failed to create volume: Invalid JWT token: signature is invalid (client and server secrets may not match)
  

• Why are these errors showing up? How to fix them?