@Frederic Garcia

A few things to check.

1.  In 2017 under Files view you can clarify what the name of the file type it is that you are using.
Mine is just an example


Please ensure it is this file type that you are exporting then importing.

2. The in  2019 under Files view please clarify what the file type name is as I assume it may not be what you see in 2017.
Which the leads me to point number 3

3. In 2019, ensure that this file type is correct listed under File - Options - File Types and that no overlapping/duplicate extensions are taking priority
In my case I have 2 txt file types and it could be the wrong one is being used at the time of file processing
FYI: The one on top will always take priority



4. Which takes me to my last point, how are your files being opened?
Via Single Document or via a project template?

If via a project template you will need to take care that point 2 is reviewed carefully and your template in 2019 may not have the correct file type support.

I trust these 4  points will help you source the root issue. If not please update post so I can help further

Lyds 

Dear Lyds,

Thank you so much for your help!

I carefully checked each one of your points, and it occurs that Studio 2019 considered my files as Plain Text v1.0.0.0 and not as Copy of Delimited Text v2.0.0.0, despite the fact that I had created a proper filetype and put it on top of the list.

I unckecked all TXT filetypes but mine, and my files for translation could not open (because Studio did non consider them as of the same type of my filetype).

Therefore, I created a new filetype again, leaving all other TXT filetypes unchecked, but this time, I did not name my filetype extension as "CLIENT.txt", I kept ".txt" only and my files for translation opened correctly!

Everything is ok now.

Thank you again Lyds!

Best regards,

Rachel (through "Frederic Garcia" account)

Glad I could help