&1 between &2 and &3 has no type

What causes this issue?

You have tried to create an iPPE relationship between the objects &v2&
and &v3&. No type has been specified for this relationship.

System Response

You can create iPPE relationships in the system only if the
relationship has been assigned to a defined type in Customizing. The
system refuses to create relationships whose types cannot be checked in
Customizing.

How to fix this error?

Select a type.

Procedure for System Administrators

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.