The two primary causes of this error are:
1. When an account is being added with a Salesforce Account ID that already exists in the system.
Troubleshooting: Please check the Salesforce Account ID and see if it is already in use.
2. Saving a Client who has not yet had a SuccessCycle selected.
Troubleshooting: Select a SuccessCycle for this Client
If you're still unable to resolve this issue, please reach out to firstname.lastname@example.org