TIBCO Scribe® Online works with the concept that only one Cloud Agent is allowed per Organization. Since your Solutions are tied to your existing Cloud Agent you will be unable to delete the existing Agent until you assign your solutions to an On-Premise Agent.
Resolution
If you find that you want to delete your Cloud Agent to move your Solutions to a new Cloud Agent, use these instructions.
Install an On-Premise Agent.
Open each Solution associated with the Cloud Agent and select the On-Premise Agent.
When all Solutions have been updated, delete the existing Cloud Agent.
Install a new Cloud Agent.
Open each Solution and select the new Cloud Agent.
Delete/uninstall the On-Premise Agent.
Issue/Introduction
Instructions to delete a TIBCO Scribe® Online Cloud Agent