Can't use/update own TM in customers Studio package

 I get the message below when adding own TM (Duits Nederlands) into a package wich I received from a customer:

 

“This translation memory ‘DUITS NEDERLANDS’ will not be used for the following language pairs:  

German (Germany) -> Dutch (Netherlands)

To edit the translation memories used for these language pairs, go tot he individual language pair level."

 

Any help is welcome, thank you all.

 

Regards,

Rudi