Diagnosis
You want data of entity type &V1& to be read. But you have limited yourselection to entity type &V2&, which acts as an additional key in adependent entity type.
The system could only consider this restriction if at least one of thefollowing conditions were fulfilled:

• There is only one dependent entity type in which the entity type &V2&
acts as an additional key.

• The entity types, in which entity type &V2& acts as an additional key,
are all dependent on exactly one other entity type in which entity typeV2 also acts as an additional key.

• An attribute of one of the dependent entity types, in which entity type
V2 acts as an additional key, is also limited further.
For the current search query, none of these conditions are met.

Procedure
Restrict further to an attribute of one of the dependent entity types,in which entity type &V2& acts as an additional key.