I'm stuck in the middle of switching from single-org to multi org. 

In **Marketing Cloud Setup** > **Salesforce Integration**, I am getting the following error: 

> 
> An exception occurred while saving the integration.
> 
> 
> 

[![enter image description here](https://i.stack.imgur.com/Y6VIN.png)](https://i.stack.imgur.com/Y6VIN.png)

I am aware that it usually has something to do with the Sales Cloud API user's permissions, so I verified that the following:

* Marketing Cloud Connected App permission set has been assigned
* Marketing Cloud for AppExchange Admin flag is checked on user
* Marketing Cloud for AppExchange User flag is also checked

I cleared out user mappings and OAuth tokens in Sales Cloud for all my API users. Didn't have any problems with establishing the connection from Sales Cloud to Marketing Cloud.

I also verified that we have white-listed all [Salesforce IP ranges](https://help.salesforce.com/articleView?id=mc_es_whitelist_ip_addresses_for_salesforce_managed_packages.htm&type=5) for the Salesforce integration.

Any clues what might be missing here?