multiple signers

Here is the signing flow steps for one of our templates:

1. Sender initiates and signs

2. Second Signs

3. Third Signs

4. Fourth Signs

5. Sender Signs

6. Fourth Signs - complete

Problem: A notification is sent for step 5. The sender logs in to sign and receives an error notification - 

"You are currently logged in as xxxx@xxxx.com. In order to view your document, please logout of this account."

The Sender can not sign the form logged into their Adobe Sign account.

Step 6 is having the same issue.

Help?