Trados 2015 Error message: "Target language does not match the expected project language

Hello everyone, 

I was sent a few xliff files to translate, but both the target and the source language are set to EN-US so, I get the error message "Target language does not match the expected project language".

I have checked the forum already for suggested solutions on these pages:

https://community.rws.com/product-groups/translationproductivity/f/studio/10782/trados-2017-error-message-target-language-does-not-match-the-expected-project-language

https://community.rws.com/product-groups/translationproductivity/f/studio/10782/trados-2017-error-message-target-language-does-not-match-the-expected-project-language

but none seemed to work for me, I still have the same problem. I cant open the files in any way - either as a single file translation or in a project. 

How can I tackle this?

Thanks