Running Bamboo 6.8.3 on Server.
User/Developer is trying to roll back a deployment to a prior version.
When they (or I) click "Start Deployment" the following message appears in a pop up window:
An unexpected error has occurred
Please supply a planKey
Please try reloading the page.
The standard deployments work fine. Clicking on Reload Page displays the same error. Clicking on Cancel returns to the prior screen stating "The release you specified does not exist" yet the release is still available.

Any thoughts would be appreciated.