This can happen for 2 reasons...
1. There is bad data in the record or data hasn't sync'd across properly.
Solution: Try doing a "Sync All" (and restarting myPractice if needed)
2. When a Referrer is added to a Referral the Referrers Provider ID is appended to their name.
If there is no Provider ID for any Referrer in the referrers table the big red X appears.
Solution: In Data Maintenance > referrers > filter for any Referrer with a blank provider ID field.
Enter in something, like "No ID Provided" in the field.
Click Apply and Ok
Reload the Client Details by Clicking Go
The Referrals should now be visible.
If the problem continues you may need to check for null data in the referrers table and replace with characters.