Diagnosis
The 'Entry Indicator Intermediate Recipient' in table 'DominanceIndicator per Document Type/Recipient Type' is initial for
Document Type: &V1&
Movement Type: &v2&
Sender Type: &v3&
Recipient Type: &v4&
Therefore, you cannot enter an intermediate recipient.

Procedure
If the entry is incorrect, you can modify it in Customizing.
Execute Function